195486472
Environmental influences on acoustic divergence in Rhinolophus bats of the Western Ghats-Sri Lanka region
According to the acoustic adaptation hypothesis, environmental and biogeographic factors such as atmospheric humidity can influence divergence of acoustic signals and speciation in high duty-cycle echolocating bats (e.g. Rhinolophus sp.), although this remains disputed. In this study we tested the hypothesis that Resting Frequency (RF) would decrease with increasing humidity along a large latitudinal gradient (6°-21° N), for four Rhinolophus species with different evolutionary histories, in the Western Ghats-Sri Lanka (WGSL) region. We conducted acoustic recordings and compiled published information on RFs of stationary Rhinolophus indorouxi, R. rouxi, R. beddomei, and R. lepidus from 40 roosts in 18 localities of the WGSL. These data comprised of recordings made with different devices and with different settings. Hence, due to the unknown measurement error involved in the recorded RFs, it was not possible to conduct conventional regression analyses to test our hypotheses. Hence, we qualitatively assessed effects of Relative Humidity (RH) and other environmental variables by interpreting only the sign, but not the magnitude of the RF responses (from the slopes of generalized least squares regression models). We also tested how RF and RH varied across biogeographic zones, and with bat body size. RFs of the Miocene-diverged species R. indorouxi and R. rouxi were higher at lower RH, as expected. In contrast, RF of the Pleistocene-diverged species R. beddomei and R. lepidus were higher at higher RH. Elevation and rainfall also emerged as important predictors of RF variation in these species. Bat body size differed in dry and humid regions of the WGSL. RF variation was not consistent across biogeographic zones. The cryptic, phonically differentiated sibling species R. indorouxi and R. rouxi co-occurred only in mid-elevation zones along the Western Ghats escarpment. The variable but significant influences of humidity and correlated factors on RF suggest the importance of environmentally mediated acoustic divergence in different Rhinolophus species in the WGSL. We propose some hypotheses on interacting effects of environmental and phylogenetic factors on acoustic divergence in Rhinolophus bats of the WGSL. These ideas could be further tested with phylogenetic and acoustic studies, as more consistent and comparable data on these species become available in the future.
9845298
Ecology and the origin of species.
The ecological hypothesis of speciation is that reproductive isolation evolves ultimately as a consequence of divergent natural selection on traits between environments. Ecological speciation is general and might occur in allopatry or sympatry, involve many agents of natural selection, and result from a combination of adaptive processes. The main difficulty of the ecological hypothesis has been the scarcity of examples from nature, but several potential cases have recently emerged. I review the mechanisms that give rise to new species by divergent selection, compare ecological speciation with its alternatives, summarize recent tests in nature, and highlight areas requiring research.
8382000
Evolutionary divergence in acoustic signals: causes and consequences.
Acoustic signals mediate mate choice, resource defense, and species recognition in a broad range of taxa. It has been proposed, therefore, that divergence in acoustic signals plays a key role in speciation. Nonetheless, the processes driving divergence of acoustic traits and their consequences in terms of speciation are poorly understood. A review of empirical and comparative studies reveals strong support for a role of sexual selection in acoustic divergence, but the possible concomitant influences of ecological context are rarely examined. We summarize a conceptual framework for testing the relative significance of both adaptive and neutral mechanisms leading to acoustic divergence, predictions for cases where these processes lead to speciation, and how their relative importance plays out over evolutionary time.
941124
Pattern, process and geographic modes of speciation
The tradition of classifying cases of speciation into discrete geographic categories (allopatric, parapatric and sympatric) fuelled decades of fruitful research and debate. Not surprisingly, as the science has become more sophisticated, this simplistic taxonomy has become increasingly obsolete. Geographic patterns are now reasonably well understood. Sister species are rarely sympatric, implying that sympatric speciation, it its most general sense, is rare. However, sympatric speciation, even in its most restricted population genetic sense, is possible. Several case studies have demonstrated that divergence has occurred in nature without geographic barriers to gene flow. Obviously, different sets of criteria for sympatric speciation will lead to different numbers of qualifying cases. But changing the rules of nomenclature to make ‘sympatric speciation’ more or less common does not constitute scientific progress. Advances in the study of speciation have come from studies of the processes that constrain or promote divergence, and how they are affected by geography.
3101762
The evolution of echolocation in bats.
Recent molecular phylogenies have changed our perspective on the evolution of echolocation in bats. These phylogenies suggest that certain bats with sophisticated echolocation (e.g. horseshoe bats) share a common ancestry with non-echolocating bats (e.g. Old World fruit bats). One interpretation of these trees presumes that laryngeal echolocation (calls produced in the larynx) probably evolved in the ancestor of all extant bats. Echolocation might have subsequently been lost in Old World fruit bats, only to evolve secondarily (by tongue clicking) in this family. Remarkable acoustic features such as Doppler shift compensation, whispering echolocation and nasal emission of sound each show multiple convergent origins in bats. The extensive adaptive radiation in echolocation call design is shaped largely by ecology, showing how perceptual challenges imposed by the environment can often override phylogenetic constraints.
54019047
Acoustic signals and speciation: the roles of natural and sexual selection in the evolution of cryptic species
In 1768, Gilbert White, a pioneer of natural history studies, wrote to fellow naturalist Thomas Pennant about warblers singing near his home at Selborne: “I have now, past dispute, made out three distinct species of the willow-wrens. . . . which constantly and invariably use distinct notes” (White, 1813). White was referring to three species of warblers in the genus Phylloscopus-the chiffchaff, P. collybita, the willow warbler, P. trochilus, and the wood warbler, P. sibilutrix. The three warblers look so similar superficially, that it was not until 30 years after White’s acute study of their different songs that they were described as different species. In Europe, the marsh tit, Parus palustris, and willow tit, P. rnontunus, are similar in appearance, but are separated easily by voice. The treecreeper, Certhia familiaris, and the short-toed treecreeper, C. brachydactylu, are almost identical to our eyes, yet their calls are quite different. Many animal species may remain undescribed because, although they seem indistinguishable from described species by their appearance, they maintain reproductive isolation by cues that are not so obvious to our senses. To humans, many animal species look similar, yet sound different. Humans have considerable visual abilities over a wide range of light wavelengths, and animals can be classified with ease according to visual criteria. Although humans also have considerable auditory skills, especially between 500 Hz and 3 kHz, differences in acoustic signals are more difficult to quantify than differences in appearance. Vocalizations must be studied in living animals, while visual differences can be assessed by examination of museum specimens. Acoustic signals can be difficult to locate, especially
86572207
Genetic divergence between morphologically and acoustically cryptic bats: novel niche partitioning or recent contact?
Molecular tools have confirmed the presence of morphologically cryptic bat species initially detected by divergent echolocation calls. Here we document the presence of two sympatric, genetically distinct populations of bats whose echolocation calls were similar in peak frequency. They differed only slightly with respect to size, skull and wing morphology, and noseleaf shape, but the individuals, all initially identified as Rhinolophus arcuatus, fell into two groups exhibiting 3–4% sequence divergence in the cytochrome b gene. The coexistence of cryptic bats with only modest echolocation and physical differences challenges our understanding of niche partitioning in rhinolophid bats and suggests the possibility that a novel mode of niche partitioning may be used. Alternatively, their distributions may have only recently intersected as a result of forest loss, especially in the lowlands.
25912843
The Divergence of Echolocation Frequency in Horseshoe Bats: Moth Hearing, Body Size or Habitat?
A phylogenetic approach was used to test three hypotheses regarding the evolution of diversity in the echolocation frequencies used by horseshoe bats (family Rhinolophidae, genus Rhinolophus): 1) Allotonic Frequency Hypothesis (high frequency echolocation in the Rhinolophidae resulted from coevolution with moth hearing); 2) Allometry Hypothesis (echolocation frequency is negatively scaled with body size and evolutionary changes in echolocation frequencies are correlated with changes in body size in the Rhinolophidae); and 3) Foraging Habitat Hypothesis (evolution of echolocation frequency is associated with changes in habitat type). Both discrete and continuous character sets were used for ancestral state reconstructions and for investigating patterns of evolution between frequency and body size, and frequency and habitat type. Contrary to the prediction of the Allotonic Frequency Hypothesis, echolocation frequency in the Rhinolophidae did not increase over time, which would be expected if moth hearing and bat echolocation frequency coevolved. The number of extant species that exhibit calls within moth hearing ranges was not significantly different from the number of species that echolocate outside of moth hearing range. There was also no correlation between changes in frequency and changes in habitat type as predicted by the Foraging Habitat Hypothesis. Instead, the evolution of echolocation frequency within the Rhinolophidae was correlated with changes in body size as predicted by the Allometry Hypothesis.
3962569
Diversification and reproductive isolation: cryptic species in the only New World high-duty cycle bat, Pteronotus parnellii
BackgroundMolecular techniques are increasingly employed to recognize the presence of cryptic species, even among commonly observed taxa. Previous studies have demonstrated that bats using high-duty cycle echolocation may be more likely to speciate quickly. Pteronotus parnellii is a widespread Neotropical bat and the only New World species to use high-duty cycle echolocation, a trait otherwise restricted to Old World taxa. Here we analyze morphological and acoustic variation and genetic divergence at the mitochondrial COI gene, the 7th intron region of the y-linked Dby gene and the nuclear recombination-activating gene 2, and provide extensive evidence that P. parnellii is actually a cryptic species complex.ResultsCentral American populations form a single species while three additional species exist in northern South America: one in Venezuela, Trinidad and western Guyana and two occupying sympatric ranges in Guyana and Suriname. Reproductive isolation appears nearly complete (only one potential hybrid individual found). The complex likely arose within the last ~6 million years with all taxa diverging quickly within the last ~1-2 million years, following a pattern consistent with the geological history of Central and northern South America. Significant variation in cranial measures and forearm length exists between three of the four groups, although no individual morphological character can discriminate these in the field. Acoustic analysis reveals small differences (5–10 kHz) in echolocation calls between allopatric cryptic taxa that are unlikely to provide access to different prey resources but are consistent with divergence by drift in allopatric species or through selection for social recognition.ConclusionsThis unique approach, considering morphological, acoustic and multi-locus genetic information inherited maternally, paternally and bi-parentally, provides strong support to conclusions about the cessation of gene flow and degree of reproductive isolation of these cryptic species.
92282226
High Duty Cycle Echolocation May Constrain the Evolution of Diversity within Horseshoe Bats (Family: Rhinolophidae)
The phenotype of organisms is the net result of various evolutionary forces acting upon their lineages over time. When an innovative trait arises that confers a substantial advantage in terms of survival and reproduction, the evolution of adaptive complexes between such an innovation and other traits may constrain diversification of that lineage. The specialized echolocation system of the Rhinolophidae may represent such an innovation which affects other parts of the phenotype. We investigated a potential constraint on the diversity of phenotypes of several species of horseshoe bats within a phylogenetic framework. If phenotypic convergence stems from stasis as a result of the specialized echolocation system, phenotypes should converge not only among members of the same species and between sexes but also among species. We analyzed the phenotypic diversity of >800 individuals of 13–16 species. The phenotypes in the horseshoe bats did indeed converge. There was no sexual size dimorphism in mass, forearm length and wingspan within species and there was marked interspecific similarity in both wing and echolocation variables but marked variability in body mass. Furthermore, correlations of wing and echolocation variables with mass suggest that variability within horseshoe bats was largely the result of selection on body size with allometric responses in wing and echolocation parameters, a potential consequence of constraints imposed by their specialized echolocation.
3793064
Variability in Echolocation Call Intensity in a Community of Horseshoe Bats: A Role for Resource Partitioning or Communication?
Background Only recently data on bat echolocation call intensities is starting to accumulate. Yet, intensity is an ecologically crucial parameter, as it determines the extent of the bats' perceptual space and, specifically, prey detection distance. Interspecifically, we thus asked whether sympatric, congeneric bat species differ in call intensities and whether differences play a role for niche differentiation. Specifically, we investigated whether R. mehelyi that calls at a frequency clearly above what is predicted by allometry, compensates for frequency-dependent loss in detection distance by using elevated call intensity. Maximum echolocation call intensities might depend on body size or condition and thus be used as an honest signal of quality for intraspecific communication. We for the first time investigated whether a size-intensity relation is present in echolocating bats. Methodology/Principal Findings We measured maximum call intensities and frequencies for all five European horseshoe bat species. Maximum intensity differed among species largely due to R. euryale. Furthermore, we found no compensation for frequency-dependent loss in detection distance in R. mehelyi. Intraspecifically, there is a negative correlation between forearm lengths and intensity in R. euryale and a trend for a negative correlation between body condition index and intensity in R. ferrumequinum. In R. hipposideros, females had 8 dB higher intensities than males. There were no correlations with body size or sex differences and intensity for the other species. Conclusions/Significance Based on call intensity and frequency measurements, we estimated echolocation ranges for our study community. These suggest that intensity differences result in different prey detection distances and thus likely play some role for resource access. It is interesting and at first glance counter-intuitive that, where a correlation was found, smaller bats called louder than large individuals. Such negative relationship between size or condition and vocal amplitude may indicate an as yet unknown physiological or sexual selection pressure.
53273551
Listening carefully: increased perceptual acuity for species discrimination in multispecies signalling assemblages
Communication is a fundamental component of evolutionary change because of its role in mate choice and sexual selection. Acoustic signals are a vital element of animal communication and sympatric species may use private frequency bands to facilitate intraspecific communication and identification of conspecifics (acoustic communication hypothesis, ACH). If so, animals should show increasing rates of misclassification with increasing overlap in frequency between their own calls and those used by sympatric heterospecifics. We tested this on the echolocation of the horseshoe bat, Rhinolophus capensis, using a classical habituation–dishabituation experiment in which we exposed R. capensis from two phonetic populations to echolocation calls of sympatric and allopatric horseshoe bat species (Rhinolophus clivosus and Rhinolophus damarensis) and different phonetic populations of R. capensis. As predicted by the ACH, R. capensis from both test populations were able to discriminate between their own calls and calls of the respective sympatric horseshoe bat species. However, only bats from one test population were able to discriminate between calls of allopatric heterospecifics and their own population when both were using the same frequency. The local acoustic signalling assemblages (ensemble of signals from sympatric conspecifics and heterospecifics) of the two populations differed in complexity as a result of contact with other phonetic populations and sympatric heterospecifics. We therefore propose that a hierarchy of discrimination ability has evolved within the same species. Frequency alone may be sufficient to assess species membership in relatively simple acoustic assemblages but the ability to use additional acoustic cues may have evolved in more complex acoustic assemblages to circumvent misidentifications as a result of the use of overlapping signals. When the acoustic signal design is under strong constraints as a result of dual functions and the available acoustic space is limited because of co-occurring species, species discrimination is mediated through improved sensory acuity in the receiver.
320004
Resource partitioning of sonar frequency bands in rhinolophoid bats
SummaryIn the Constant Frequency portions of the orientation calls of various Rhinolophus and Hipposideros species, the frequency with the strongest amplitude was studied comparatively. (1) In the five European species of the genus Rhinolophus call frequencies are either species-specific (R. ferrumequinum, R. blasii and R. euryale) or they overlap (R. hipposideros and R. mehelyi). The call frequency distributions are approximately 5–9 kHz wide, thus their ranges spead less than ±5% from the mean (Fig. 1). Frequency distributions are considerably narrower within smaller geographic areas. (2) As in other bat groups, call frequencies of the Rhinolophoidea are negatively correlated with body size (Fig. 3). Regression lines for the genera Rhinolophus and Rhinolophus, species from dryer climates have on the average higher call frequencies than species from tropical rain forests. (4) The Krau Game Reserve, a still largely intact rain forest area in Malaysia, harbours at least 12 syntopic Rhinolophus and Hipposiderso species. Their call frequencies lie between 40 and 200 kHz (Fig. 2). Distribution over the available frequency range is significantly more even than could be expected from chance alone. Two different null hypotheses to test for random character distribution were derived from frequency-size-relations and by sampling species assemblages from a species pool (Monte Carlo method); both were rejected. In particular, call frequencies lying close together are avoided (Figs. 4, 5). Conversely, the distribution of size ratios complied with a corresponding null hypothesis. This even distribution may be a consequence of resource partitioning with respect to prey type. Alternatively, the importance of these calls as social signals (e.g. recognition of conspecifics) might have necessitated a communication channel partitioning.
7750940
Resource partitioning in rhinolophoid bats revisited
Abstract We assessed the ecomorphological structure of a guild of rhinolophoid bats in a Malaysian rainforest first described by Heller and von Helversen (1989). These authors found that the distribution of echolocation call frequencies used by 12 syntopic species was more even than expected from allometric relationships or in randomly generated communities, and that the observed minimal ratio was greater than expected by chance alone. In this study we were able to expand their guild to 15 species, but in doing so it became apparent that call frequencies might be less evenly distributed across the total frequency range than previously proposed. We replicated Heller and von Helversen’s (1989) analyses with the full 15-species complement but were unable to support their suggestion that rhinolophoid bats exhibit resource partitioning through differences in frequency bands. We adopted a multivariate approach and incorporated measures of body size and wing morphology into the analysis. We used phylogenetic autocorrelation to ensure that the species were statistically independentand principal component analysis to describe the morphological space occupied by the 15 species in the community and four additional species representing the extremes of phenotypic variation. We derived interspecific Euclidean distances and tested the mean values and SDs of these distances against those of 100 guilds of ”synthetic” species created randomly within the principal component space. The guild of Rhinolophoidea was not distributed randomly in multivariate space. Instead we found evidence of morphological overdispersion of the most similar species, which suggests niche differentiation in response to competition. Less similar species were nearer in morphological space than expected, and we suggest this is a consequence of ecological constraints on parameter combinations. Despite this underdispersion, many of the more distant neighbours were evenly rather than randomly spaced or clumped in morphospace, suggesting that, given the environmental constraints on morphology, species in this guild do experience limits to their similarity. Finally, we tested the influence of the relative abundance of species on morphological displacement, and found no evidence that abundant, spatially correlated species reduce interspecific overlap in morphological space.
50789553
It’s not all about the Soprano: Rhinolophid bats use multiple acoustic components in echolocation pulses to discriminate between conspecifics and heterospecifics
Acoustic communication plays a pivotal role in conspecific recognition in numerous animal taxa. Vocalizations must therefore have discrete acoustic signatures to facilitate intra-specific communication and to avoid misidentification. Here we investigate the potential role of echolocation in communication in horseshoe bats. Although it has been demonstrated that echolocation can be used to discriminate among con- and hetero-specifics, the specific acoustic cues used in discrimination are still relatively unknown. Furthermore, the Acoustic Communication Hypothesis proposes that in multispecies assemblages, in which echolocation frequencies are likely to overlap, bats partition acoustic space along several dimensions so that each species occupies a discrete communication domain. Thus, multiple echolocation variables may be used in discrimination. The objective of this study was to investigate the potential of various echolocation variables to function as discriminatory cues in echolocation-based species discrimination. Using habituation–dishabituation playback experiments, we firstly tested the ability of Rhinolophus clivosus to discriminate between echolocation pulses of heterospecifics with either discrete or overlapping frequencies. Secondly, to determine whether R. clivosus could use echolocation variables other than frequency, we investigated its ability to discriminate among echolocation pulses differing in only one manipulated parameter. These test variables were identified by their contribution to the dissimilarity among pulses. Our results suggest that R. clivosus could discriminate readily between species using echolocation pulses with discrete frequencies. When frequencies overlapped, the ability of bats to discriminate was dependant on additional acoustic variables that defined the acoustic space occupied by the test signal. These additional acoustic variables included, but may not be restricted to, sweep rate of the FM and duty cycle. Thus, when echolocation pulses share a similar acoustic domain, bats use several cues to reliably discriminate among heterospecifics.
84554088
Variable resonance in constant frequency bats
Bats of the two closely related families Rhinolophidae and Hipposideridae, and also Chilonycteris rubiginosa of the family Phyllostomatidae, emit echo-location pulses with a relatively long portion of constant frequency followed by a rapid frequency sweep. The greatest amplitude occurs either during the constant frequency or at some point in the sweep with the constant frequency at a lower amplitude. Two hypotheses are advanced to account for the changes in frequency of peak amplitude: a variable vocal tract resonance or “source generated” amplitude changes, and their relative merits are considered. The importance to the animals of high amplitude frequency sweeps is discussed, considering the conditions under which they are produced and whether the echoes from such pulses can be detected.
86298286
Horseshoe Bats Recognise the Sex of Conspecifics from Their Echolocation Calls
Echolocation calls produced by bats contain information on the emitter that could be used in social interactions. Nevertheless, little is known about the whether such information actually is being used by bats. Here we tested the ability of two horseshoe bat species (Rhinolophus mehelyi and R. euryale; n = 20 each) to discriminate conspecific male from conspecific female echolocation calls and vice versa. Behavioural data from a habituation-discrimination paradigm revealed that both species were able to recognize the sex of conspecifics from their calls, providing evidence that cues on the sex of the emitter are encoded in echolocation signals. While our data support that the sex-specific acoustic cues are not (just) the horseshoe bats' constant-frequency call part, their nature remains enigmatic. This is the second study to show that bats can recognize the caller's gender from echolocation calls and the first to do so for ‘high-duty-cycle bats’; those that use calls with a prominent constant-frequency (CF) component.
3938908
Phenotypic Convergence in Genetically Distinct Lineages of a Rhinolophus Species Complex (Mammalia, Chiroptera)
Phenotypes of distantly related species may converge through adaptation to similar habitats and/or because they share biological constraints that limit the phenotypic variants produced. A common theme in bats is the sympatric occurrence of cryptic species that are convergent in morphology but divergent in echolocation frequency, suggesting that echolocation may facilitate niche partitioning, reducing competition. If so, allopatric populations freed from competition, could converge in both morphology and echolocation provided they occupy similar niches or share biological constraints. We investigated the evolutionary history of a widely distributed African horseshoe bat, Rhinolophus darlingi, in the context of phenotypic convergence. We used phylogenetic inference to identify and date lineage divergence together with phenotypic comparisons and ecological niche modelling to identify morphological and geographical correlates of those lineages. Our results indicate that R. darlingi is paraphyletic, the eastern and western parts of its distribution forming two distinct non-sister lineages that diverged ~9.7 Mya. We retain R. darlingi for the eastern lineage and argue that the western lineage, currently the sub-species R. d. damarensis, should be elevated to full species status. R. damarensis comprises two lineages that diverged ~5 Mya. Our findings concur with patterns of divergence of other co-distributed taxa which are associated with increased regional aridification between 7-5 Mya suggesting possible vicariant evolution. The morphology and echolocation calls of R. darlingi and R. damarensis are convergent despite occupying different biomes. This suggests that adaptation to similar habitats is not responsible for the convergence. Furthermore, R. darlingi forms part of a clade comprising species that are bigger and echolocate at lower frequencies than R. darlingi, suggesting that biological constraints are unlikely to have influenced the convergence. Instead, the striking similarity in morphology and sensory biology are probably the result of neutral evolutionary processes, resulting in the independent evolution of similar phenotypes.
2126549
Determinants of echolocation call frequency variation in the Formosan lesser horseshoe bat (Rhinolophus monoceros)
The origin and maintenance of intraspecific variation in vocal signals is important for population divergence and speciation. Where vocalizations are transmitted by vertical cultural inheritance, similarity will reflect co-ancestry, and thus vocal divergence should reflect genetic structure. Horseshoe bats are characterized by echolocation calls dominated by a constant frequency component that is partly determined by maternal imprinting. Although previous studies showed that constant frequency calls are also influenced by some non-genetic factors, it is not known how frequency relates to genetic structure. To test this, we related constant frequency variation to genetic and non-genetic variables in the Formosan lesser horseshoe bat (Rhinolophus monoceros). Recordings of bats from across Taiwan revealed that females called at higher frequencies than males; however, we found no effect of environmental or morphological factors on call frequency. By comparison, variation showed clear population structure, with frequencies lower in the centre and east, and higher in the north and south. Within these regions, frequency divergence was directional and correlated with geographical distance, suggesting that call frequencies are subject to cultural drift. However, microsatellite clustering analysis showed that broad differences in constant frequency among populations corresponded to discontinuities in allele frequencies resulting from vicariant events. Our results provide evidence that the processes shaping genetic subdivision have concomitant consequences for divergence in echolocation call frequency.
4236059
Geographic Variation in the Acoustic Traits of Greater Horseshoe Bats: Testing the Importance of Drift and Ecological Selection in Evolutionary Processes
Patterns of intraspecific geographic variation of signaling systems provide insight into the microevolutionary processes driving phenotypic divergence. The acoustic calls of bats are sensitive to diverse evolutionary forces, but processes that shape call variation are largely unexplored. In China, Rhinolophus ferrumequinum displays a diverse call frequency and inhabits a heterogeneous landscape, presenting an excellent opportunity for this kind of research. We quantified geographic variation in resting frequency (RF) of echolocation calls, estimated genetic structure and phylogeny of R. ferrumequinum populations, and combined this with climatic factors to test three hypotheses to explain acoustic variation: genetic drift, cultural drift, and local adaptation. Our results demonstrated significant regional divergence in frequency and phylogeny among the bat populations in China's northeast (NE), central-east (CE) and southwest (SW) regions. The CE region had higher frequencies than the NE and SW regions. Drivers of RF divergence were estimated in the entire range and just the CE/NE region (since these two regions form a clade). In both cases, RF divergence was not correlated with mtDNA or nDNA genetic distance, but was significantly correlated with geographic distance and mean annual temperature, indicating cultural drift and ecological selection pressures are likely important in shaping RF divergence among different regions in China.
86463441
Geographical and individual variation in echolocation calls of the intermediate leaf‐nosed bat, Hipposideros larvatus
The cause and significance of variation in echolocation call frequency within hipposiderid bats is not well understood despite an increasing number of allopatric and sympatric examples being documented. We examined variation patterns in the resting frequency (RF) of echolocation calls emitted by the intermediate leaf-nosed bat, Hipposideros larvatus, on a broad geographical scale. Data mining technology and Kruskal–Wallis test both showed substantial variation with a longitudinal pattern in RF in H. larvatus among colonies, and this variation was associated with geographical distance and not body size. In addition, we found that a high degree of variability between individuals was hidden under the geographical variation. The results support an effect of random cultural drift, and challenge the prey detection hypothesis. Moreover, an acoustic difference among local island colonies may be indicative of a vocal dialect. We found that each colony of H. larvatus seems to maintain a ‘private bandwidth’, which could be used for colony identity and individual communication thus helping individuals and colonies to get a number of fitness benefits.
11740345
Sensory trait variation in an echolocating bat suggests roles for both selection and plasticity
BackgroundAcross heterogeneous environments selection and gene flow interact to influence the rate and extent of adaptive trait evolution. This complex relationship is further influenced by the rarely considered role of phenotypic plasticity in the evolution of adaptive population variation. Plasticity can be adaptive if it promotes colonization and survival in novel environments and in doing so may increase the potential for future population differentiation via selection. Gene flow between selectively divergent environments may favour the evolution of phenotypic plasticity or conversely, plasticity itself may promote gene flow, leading to a pattern of trait differentiation in the presence of gene flow. Variation in sensory traits is particularly informative in testing the role of environment in trait and population differentiation. Here we test the hypothesis of ‘adaptive differentiation with minimal gene flow’ in resting echolocation frequencies (RF) of Cape horseshoe bats (Rhinolophus capensis) across a gradient of increasingly cluttered habitats.ResultsOur analysis reveals a geographically structured pattern of increasing RF from open to highly cluttered habitats in R. capensis; however genetic drift appears to be a minor player in the processes influencing this pattern. Although Bayesian analysis of population structure uncovered a number of spatially defined mitochondrial groups and coalescent methods revealed regional-scale gene flow, phylogenetic analysis of mitochondrial sequences did not correlate with RF differentiation. Instead, habitat discontinuities between biomes, and not genetic and geographic distances, best explained echolocation variation in this species. We argue that both selection for increased detection distance in relatively less cluttered habitats and adaptive phenotypic plasticity may have influenced the evolution of matched echolocation frequencies and habitats across different populations.ConclusionsOur study reveals significant sensory trait differentiation in the presence of historical gene flow and suggests roles for both selection and plasticity in the evolution of echolocation variation in R. capensis. These results highlight the importance of population level analyses to i) illuminate the subtle interplay between selection, plasticity and gene flow in the evolution of adaptive traits and ii) demonstrate that evolutionary processes may act simultaneously and that their relative influence may vary across different environments.
204242723
Integrated approaches to identifying cryptic bat species in areas of high endemism: The case of Rhinolophus andamanensis in the Andaman Islands
The diversity of bats worldwide includes large numbers of cryptic species, partly because divergence in acoustic traits such as echolocation calls are under stronger selection than differences in visual appearance in these nocturnal mammals. Island faunas often contain disproportionate numbers of endemic species, and hence we might expect cryptic, endemic species to be discovered relatively frequently in bats inhabiting islands. Species are best defined when multiple lines of evidence supports their diagnosis. Here we use morphometric, acoustic, and molecular phylogenetic data to show that a horseshoe bat in the Andaman Islands is distinct in all three aspects, supporting its status as a distinct species. We recommend investigation into possible new and endemic bat species on islands by using integrated approaches that provide independent lines of evidence for taxonomic distinctiveness. We provide a formal redescription of the taxon newly raised to species level, Rhinolophus andamanensis Dobson, 1872.
83520763
Echolocation calls of Rhinolophus ferrumequinum in relation to habitat type and environmental factors
Abstract The present experiment was carried out in Luotong Mountain Natural Reserve in Jilin Province of China in 2007. We recorded and analyzed the echolocation calls of Rhinolophus ferrumequinum in different habitats by using Avisoft Bioacoustics USG 116 and Avisoft-SASLAB PRO (Avisoft Bioacoustics, Berlin, Germany). Our results showed that R. ferrumequinum foraged in diverse habitats in the study area, and their echolocation calls were significantly variable in different habitats (One-Way ANOVA, P
91542248
The Relative Roles of Selection and Drift in Phenotypic Variation: Some Like It Hot, Some Like It Wet
Acoustic signals mediate important functions, e.g. orientation, foraging and communication, that impact on the survival and reproduction of animals. The propagation of acoustic signals is also known to be influenced by habitat, particularly differences in climate. It is therefore likely that the environment would exert significant influence on such signals and that selection rather than drift would be largely responsible for geographic variation in acoustic signals. We investigated the role of selection and drift in geographic variation in the echolocation of two species of horseshoe bats Rhinolophus damarensis and R. clivosus (Rhinolophidae) with wide geographic distributions across the arid and mesic biomes of southern Africa. In both species, selection was found to be the dominant evolutionary process influencing phenotypic variation; however, there was evidence of drift in R. clivosus. Furthermore, selection was not differentially exerted across populations because there was no change in the results when localities were excluded one at a time. Population divergence appeared to be mediated by selection on traits associated with manoeuvrability, detection and size in both species despite their disparate distributions. However, the climatic factor that best explained geographic variation in echolocation was dependent on the biomes occupied by the species. Temperature was the dominant climatic factor in R. damarensis, a species with a largely arid distribution. In R. clivosus, a species with distributions across both mesic and arid biomes, temperature and relative humidity together explained variation in echolocation.
21919618
Environmental correlates of geographic divergence in a phenotypic trait: A case study using bat echolocation
Abstract Divergence in phenotypic traits may arise from the interaction of different evolutionary forces, including different kinds of selection (e.g., ecological), genetic drift, and phenotypic plasticity. Sensory systems play an important role in survival and reproduction, and divergent selection on such systems may result in lineage diversification. Such diversification could be largely influenced by selection in different environments as a result of isolation by environment (IbE). We investigated this process using geographic variation in the resting echolocation frequency of the horseshoe bat species, Rhinolophus damarensis, as a test case. Bats were sampled along a latitudinal gradient ranging from 16°S to 32°S in the arid western half of southern Africa. We measured body size and peak resting frequencies (RF) from handheld individual bats. Three hypotheses for the divergence in RF were tested: (1) James’ Rule, (2) IbE, and (3) genetic drift through isolation by distance (IbD) to isolate the effects of body size, local climatic conditions, and geographic distance, respectively, on the resting frequency of R. damarensis. Our results did not support genetic drift because there was no correlation between RF variation and geographic distance. Our results also did not support James' Rule because there was no significant relationship between (1) geographic distances and RF, (2) body size and RF, or (3) body size and climatic variables. Instead, we found support for IbE in the form of a correlation between RF and both region and annual mean temperature, suggesting that RF variation may be the result of environmental discontinuities. The environmental discontinuities coincided with previously reported genetic divergence. Climatic gradients in conjunction with environmental discontinuities could lead to local adaptation in sensory signals and directed dispersal such that gene flow is restricted, allowing lineages to diverge. However, our study cannot exclude the role of processes like phenotypic plasticity in phenotypic variation.
3862651
Correlated Genetic and Ecological Diversification in a Widespread Southern African Horseshoe Bat
The analysis of molecular data within a historical biogeographical framework, coupled with ecological characteristics can provide insight into the processes driving diversification. Here we assess the genetic and ecological diversity within a widespread horseshoe bat Rhinolophus clivosus sensu lato with specific emphasis on the southern African representatives which, although not currently recognized, were previously described as a separate species R. geoffroyi comprising four subspecies. Sequence divergence estimates of the mtDNA control region show that the southern African representatives of R. clivosus s.l. are as distinct from samples further north in Africa than they are from R. ferrumequinum, the sister-species to R. clivosus. Within South Africa, five genetically supported geographic groups exist and these groups are corroborated by echolocation and wing morphology data. The groups loosely correspond to the distributions of the previously defined subspecies and Maxent modelling shows a strong correlation between the detected groups and ecoregions. Based on molecular clock calibrations, it is evident that climatic cycling and related vegetation changes during the Quaternary may have facilitated diversification both genetically and ecologically.
22843415
Genetic and acoustic population structuring in the Okinawa least horseshoe bat: are intercolony acoustic differences maintained by vertical maternal transmission?
The origin and meaning of echolocation call frequency variation within rhinolophid bats is not well understood despite an increasing number of allopatric and sympatric examples being documented. A bimodal distribution of mean regional call frequency within the Okinawa‐jima Island population of Rhinolophus cornutus pumilus (Rhinolophidae) provided a unique opportunity to investigate geographic call frequency variation early in its development. Individual resting echolocation frequencies, partial mitochondrial DNA D‐loop sequences and genotypes from six microsatellite loci were obtained from 288 individuals in 11 colonies across the entire length of the island, and nearby Kume‐jima Island. Acoustic differences (5–8 kHz) observed between the north and south regions have been maintained despite evidence of sufficient nuclear gene flow across the middle of the island. Significant subdivision of maternally inherited D‐loop haplotypes suggested a limitation of movement of females between regions, but not within the regions, and was evidence of female philopatry. These results support a ‘maternal transmission’ hypothesis whereby the difference in the constant frequency (CF) component between the regions is maintained by mother–offspring transmission of CF, the restricted dispersal of females between regions and small effective population size. We suggest that the mean 5–8 kHz call frequency difference between the regions might develop through random cultural drift.
34782319
Acoustic divergence in two cryptic Hipposideros species: a role for social selection?
We present evidence that a relatively widespread and common bat from South East Asia comprises two morphologically cryptic but acoustically divergent species. A population of the bicoloured leaf–nosed bat (Hipposideros bicolor) from Peninsular Malaysia exhibits a bimodal distribution of echolocation call frequencies, with peaks in the frequency of maximum energy at ca. 131 and 142 kHz. The two phonic types are genetically distinct, with a cytochrome b sequence divergence of just under 7%. We consider the mechanisms by which acoustic divergence in these species might arise. Differences in call frequency are not likely to effect resource partitioning by detectable prey size or functional range. However, ecological segregation may be achieved by differences in microhabitat use; the 131 kHz H. bicolor is characterized by significantly longer forearms, lower wing loading, a lower aspect ratio and a more rounded wingtip, features that are associated with greater manoeuvrability in flight that may enable it to forage in more cluttered environments relative to the 142 kHz phonic type. We suggest that acoustic divergence in these species is a consequence of social selection for a clear communication channel, which is mediated by the close link between the acoustic signal and receptor systems imposed by the highly specialized nature of the hipposiderid and rhinolophid echolocation system.
9722101
Space, sympatry and speciation
Sympatric speciation remains controversial. ‘Sympatry’ originally meant “in the same geographical area”. Recently, evolutionists have redefined ‘sympatric speciation’ non‐spatially to require panmixia (m = 0.5) between a pair of demes before onset of reproductive isolation. Although panmixia is a suitable starting point in models of speciation, it is not a useful definition of sympatry in natural populations, because it becomes virtually impossible to find or demonstrate sympatry in nature. The newer, non‐spatial definition fails to address the classical debate about whether natural selection within a geographic overlap regularly causes speciation in nature, or whether complete geographic isolation is usually required. We therefore propose a more precise spatial definition by incorporating the population genetics of dispersal (or ‘cruising range’). Sympatric speciation is considerably more likely under this spatial definition than under the demic definition, because distance itself has a powerful structuring effect, even over small spatial scales comparable to dispersal. Ecological adaptation in two‐dimensional space often acts as a ‘magic trait’ that causes pleiotropic reductions of gene flow. We provide examples from our own research.
887335
Female Mate Choice Can Drive the Evolution of High Frequency Echolocation in Bats: A Case Study with Rhinolophus mehelyi
Animals employ an array of signals (i.e. visual, acoustic, olfactory) for communication. Natural selection favours signals, receptors, and signalling behaviour that optimise the received signal relative to background noise. When the signal is used for more than one function, antagonisms amongst the different signalling functions may constrain the optimisation of the signal for any one function. Sexual selection through mate choice can strongly modify the effects of natural selection on signalling systems ultimately causing maladaptive signals to evolve. Echolocating bats represent a fascinating group in which to study the evolution of signalling systems as unlike bird songs or frog calls, echolocation has a dual role in foraging and communication. The function of bat echolocation is to generate echoes that the calling bat uses for orientation and food detection with call characteristics being directly related to the exploitation of particular ecological niches. Therefore, it is commonly assumed that echolocation has been shaped by ecology via natural selection. Here we demonstrate for the first time using a novel combined behavioural, ecological and genetic approach that in a bat species, Rhinolophus mehelyi: (1) echolocation peak frequency is an honest signal of body size; (2) females preferentially select males with high frequency calls during the mating season; (3) high frequency males sire more off-spring, providing evidence that echolocation calls may play a role in female mate choice. Our data refute the sole role of ecology in the evolution of echolocation and highlight the antagonistic interplay between natural and sexual selection in shaping acoustic signals.
85694586
Genetic divergence and echolocation call frequency in cryptic species of Hipposideros larvatus s.l . (Chiroptera: Hipposideridae) from the Indo-Malayan region
The intermediate leaf-nosed bat (Hipposideros larvatus) is a medium-sized bat distributed throughout the Indo-Malay region. In north-east India, bats identified as H. larvatus captured at a single cave emitted echolocation calls with a bimodal distribution of peak frequencies, around either 85 kHz or 98 kHz. Individuals echolocating at 85 kHz had larger ears and longer forearms than those echolocating at 98 kHz, although no differences were detected in either wing morphology or diet, suggesting limited resource partitioning. A comparison of mitochondrial control region haplotypes of the two phonic types with individuals sampled from across the Indo-Malay range supports the hypothesis that, in India, two cryptic species are present. The Indian 98-kHz phonic bats formed a monophyletic clade with bats from all other regional populations sampled, to the exclusion of the Indian 85-kHz bats. In India, the two forms showed 12–13% sequence divergence and we propose that the name Hipposideros khasiana for bats of the 85-kHz phonic type. Bats of the 98-kHz phonic type formed a monophyletic group with bats from Myanmar, and corresponded to Hipposideros grandis, which is suggested to be a species distinct from Hipposideros larvatus. Differences in echolocation call frequency among populations did not reflect phylogenetic relationships, indicating that call frequency is a poor indicator of evolutionary history. Instead, divergence in call frequency probably occurs in allopatry, possibly augmented by character displacement on secondary contact to facilitate intraspecific communication.
83540634
Geographical variation in echolocation vocalizations of the Himalayan leaf‐nosed bat: contribution of morphological variation and cultural drift
Ecologists and evolutionary biologists have a long-standing interest in the patterns and causes of geographical variation in animals’ acoustic signals. Nonetheless, the processes driving acoustic divergence are still poorly understood. Here, we studied the geographical variation in echolocation vocalizations (commonly referred to as echolocation ‘pulses’ given their short duration and relatively stereotypic nature, and to contrast them from the communicative vocalizations or ‘calls’) of a widespread bat species Hipposideros armiger in south China, and assessed whether the acoustic divergence was driven by either ecological selection, or cultural or genetic drift. Our results revealed that the peak frequency of echolocation pulses varied significantly across populations sampled, with the maximum variation of about 6 kHz. The peak frequency clustered into three groups: eastern and western China, Hainan and southern Yunnan. The population differences in echolocation pulses were not significantly related to the variation in climatic (mean annual temperature, mean annual relative humidity, and mean annual precipitable water) or genetic (genetic distance) factors, but significantly related to morphological (forearm length) variation which was correlated with mean annual temperature. Moreover, the acoustic differences were significantly correlated with geographical and latitudinal distance after controlling for ‘morphological distance’. Thus, neither direct ecological selection nor genetic drift contributed to the acoustic divergence observed in H. armiger. Instead, we propose that the action of both indirect ecological selection (i.e. selection on body size) as well as cultural drift promote, in part, divergence in echolocation vocalizations of individuals within geographically distributed populations.
90560208
The effects of cultural drift on geographic variation in echolocation calls of the Chinese rufous horseshoe bat (Rhinolophus sinicus)
Drift, selection, or their combined effects commonly drive geographic variation in traits. Clarifying the relative roles of each process is a long-standing research goal in evolutionary biology. Acoustic signals of bats are a phenotypic characteristic that plays an important role in social organization and species recognition. We extensively sampled the Chinese rufous horseshoe bat (Rhinolophus sinicus) throughout China and Vietnam and reconstructed a species phylogeny to better understand the patterns and causes of the geographic variation of acoustic signals. Our results showed that the resting frequency (RF) of calls varied with latitude, sex, and distance among different colony locations. RF differences were not correlated with genetic distance (based on only one nuclear locus and the mitochondrial locus), climatic factors (mean annual temperature and mean annual precipitable water), or body size, although differences in calls increased with distance among various populations. This suggests that cultural drift may play more important roles than genetic drift and acoustic adaptation in shaping acoustic differences within regions in R. sinicus.
55171836
Ecomorphological differences between sister species, Rhinolophus capensis and Rhinolophus swinnyi
Phenotypic analyses of sibling species provide the opportunity to examine divergence that is caused by adaptation rather than phylogenetic history. RhillO/ophllS capcl/sis and Rhin%phus slrillllyi diverged from a common ancestor between 15 and 20 million years ago. The Fynbos biome of the south-western Cape (South Africa) arose around the same time, and its distribution is coincident with that of R. capclIsis. Since this event probably int1uenced the speciation of these species, I examine differences in the ecomorphology of these bats in their current distributions. R. capcnsis is bigger than R. Sll'iIlIlVi. with cOITesponding differences in echolocation call signatures and \ving morphology. Individuals from populations on the edge of the distributions of both R, capcl/sis and R. SII'illllyi are larger, and have larger wing loadings, than those further towards the centre of their ranges. The edge populations also occur with a major transition zone where a number of biomes meet. The larger body size of R. capclIsis. and of the populations at the ecotone, is probably an adaptation that provides identical benefit in both cases. Larger body sizes allow them to widen their niche width, and an increased wing loading makes commuting t1ights to adequate resources more energetically efficient. Body size was the major difference betwcen R. capcnsis and R. SH'illllyi with allometric responses in echolocation calls, as well as wing and skull morphology. 3 Un ive rsi ty of Ca pe To wn
83863788
Identifying the effects of the Pleistocene on the greater horseshoe bat, Rhinolophus ferrumequinum, in East Asia using ecological niche modelling and phylogenetic analyses
Aim  The extent to which the ranges of temperate biota in East Asia have been shaped by geological and climatic changes during the Pleistocene remains poorly understood. Previous molecular-based studies of the greater horseshoe bat (Rhinolophus ferrumequinum), which is widespread across China and Japan, suggest that this species was able to persist in multiple refugia in this region. However, limited availability of samples precluded a detailed analysis of past distributions. By integrating ecological niche modelling with phylogenetic analyses, we aim to resolve the impact of past events on the population genetic structure of R. ferrumequinum and provide detailed descriptions of potential distribution patterns during this time. 
 
 
 
Location  Central/East China and Japan. 
 
 
 
Methods  Phylogenetic analyses were carried out using 1098 bp of the mitochondrial ND2 gene and 13 microsatellite loci from bats sampled at 26 localities across China and Japan. Haplotype data were used in isolation-with-migration models (IMa) to estimate divergence dates between different lineages, and mismatch distribution analyses were undertaken to test for signs of population expansion. Geographical structuring of the microsatellite data was examined by spatial clustering. Ecological niche modelling was performed based on high-resolution palaeoclimate data inferred for the Last Glacial Maximum (LGM). 
 
 
 
Results  Phylogenetic analyses identified deep levels of divergence between three major lineages broadly corresponding to Central China, East China and Japan. The divergence of all three lineages was estimated to have occurred before the LGM. A strong correlation was observed between the ecological niche model and phylogenetic data, with both methods inferring that R. ferrumequinum populations in Central China did not undergo significant range contractions during glacial episodes. The impact of glacial cycles on East China would have been more severe, with some locations being unable to support viable populations. Zones of secondary contact were identified between Central/East China and East China/Japan, which probably result from some historical gene flow between isolated populations. 
 
 
 
Main conclusions  Integrating ecological niche modelling within phylo-geographical studies provides support for a complex demographic history for R. ferrumequinum in East Asia, as well as persistence during glacial episodes in multiple refugia across their range.
23321137
Variation in the resting frequency of Rhinolophus pusillus in Mainland China: effect of climate and implications for conservation.
This study describes variation patterns in the constant frequency of echolocation calls emitted at rest and when not flying ("resting frequency" RF) of the least horseshoe bat, Rhinolophus pusillus, on a broad geographical scale and in response to local climatic variables. Significant differences in RF were observed among populations throughout the species range in Mainland China, and this variation was positively and significantly related to climate conditions, especially environmental humidity, but the variability was only weakly associated with geographical distance. Sex dimorphism in the RF of R. pusillus may imply that female and male might keep their frequencies within a narrow range for sex recognition. Moreover, bats adjusted resting frequency to humidity, which may imply partitioning diet by prey size or the influence of rainfall noise. The results indicate that bats adjust echolocation call frequency to adapt to environmental conditions. Therefore, environmental selection shape the diversity of echolocation call structure of R. pusillus in geographically separated populations, and conservation efforts should focus on changes in local climate and effects of environmental noise.
22788602
The effect of climate on acoustic signals: does atmospheric sound absorption matter for bird song and bat echolocation?
The divergence of signals along ecological gradients may lead to speciation. The current research tests the hypothesis that variation in sound absorption selects for divergence in acoustic signals along climatic gradients, which has implications for understanding not only diversification, but also how organisms may respond to climate change. Because sound absorption varies with temperature, humidity, and the frequency of sound, individuals or species may vary signal structure with changes in climate over space or time. In particular, signals of lower frequency, narrower bandwidth, and longer duration should be more detectable in environments with high sound absorption. Using both North American wood warblers (Parulidae) and bats of the American Southwest, this work found evidence of associations between signal structure and sound absorption. Warbler species with higher mean absorption across their range were more likely to have narrow bandwidth songs. Bat species found in higher absorption habitats were more likely to have lower frequency echolocation calls. In addition, bat species changed echolocation call structure across seasons, using longer duration, lower frequency calls in the higher absorption rainy season. These results suggest that signals may diverge along climatic gradients due to variation in sound absorption, although the effects of absorption are modest.
23673171
Modelling the prey detection performance of Rhinonicteris aurantia (Chiroptera: Hipposideridae) in different atmospheric conditions discounts the notional role of relative humidity in adaptive evolution.
We examined a recent notion that differences in echolocation call frequency amongst geographic groups of constant frequency (CF)-emitting bats is the result of a trade-off between maximising prey detection range at lower frequencies and enhancing small-prey resolution at higher frequencies in different atmospheric (relative humidity; RH) environments. Isolated populations of the endemic Australian orange leaf-nosed bat Rhinonicteris aurantia were used as an example since geographic isolation in different environments has been a precursor to differences in their characteristic echolocation call frequencies (mean difference c. 6 kHz; means of 114.64 and 120.99 kHz). The influence of both atmospheric temperature and RH on maximum prey detection range was explored through mathematical modelling. This revealed that temperature was of similar importance to relative humidity and that under certain circumstances, each could reduce the effect of the other on ultrasound attenuation rates. The newly developed models contain significant conceptual improvements in method compared to other recent approaches, and can be applied to the situation of any other species of bat. For a given set of atmospheric conditions, the prey detection range of R. aurantia was reduced slightly when call frequency increased by 6 kHz, but an increase in RH, temperature or both reduced detection range significantly. A similar trend was also evident in prey detection volume ratios calculated for the same conditions. Spatial volume ratios were applied to assess the impact of changed atmospheric conditions and prey size on foraging ecology. Reductions in detection range associated with increases in RH and/or temperature also varied in relation to the size (cross sectional area) of insect prey. Modelling demonstrated that small (6 kHz) movements in call frequency could not compensate for the changes in prey detection range and spatial detection volumes that result from significant changes in atmospheric temperature or RH. The notion that differences in RH are the primary cause leading to adaptive evolution and speciation in CF-emitting bats by precipitating intraspecific differences in the mean call frequency of geographically isolated bat populations was not supported by the results of this case study.
12407294
Geographic Size Variation in Birds and Its Relationship to Climate
There is a high degree of concordance among the patterns of geographic size variation in birds in the eastern and central United States. This is demonstrated for 12 species by assuming that wing length measurements are an indicator of body size on the intraspecific level, and by arranging the data in the form of a grid of means of wing lengths for sample areas. Maps giving isophenetic lines for wing length indicate gradually increasing size dines northward and westward from Florida in the Hairy Woodpecker (Dendrocopos villosus), Downy Woodpecker (Dendrocopos pubescens), Blue Jay (Cyanocitta cristata), Carolina Chickadee (Parus carolinensis), White-breasted Nuthatch (Sitta carolinensis), and Eastern Meadowlark (Sturnella magna). In each case there is a trend for larger (or longer-winged) birds to extend southward in the Appalachian Mountains and for smaller (or shorter-winged) birds to extend northward in the Mississippi River valley. Maps made by a computer and automatic plotter using contour intervals of 0.5 mm of mean wing length for the Downy Woodpecker, for male White-breasted Nuthatches, and for female Blue Jays show that, in addition to the pattern just mentioned, relatively longer-winged birds extend southward in the interior highlands of Arkansas, and relatively shorter-winged birds extend northward up other river valleys. These subtle relationships between intraspecific size variation and topo- graphic features suggest that the link between the two phenomena may be precise adaptations to even minor climatic gradients. The relationship between these findings and the subspecies concept is discussed. Correlation coefficients for the pattern of variation in the Downy Woodpecker with seasonal and annual wet-bulb temperature, vapor pressure, and absolute humidity were all either equal to or higher than correlations with dry-bulb temperature. Since these variables reflect the combined effects of temperature and humidity, the obvious indication is that size variation is more closely related to this combination than to temperature alone. Additional correlations using the mean wing length data for seven other species confirmed that wet-bulb temperature patterns are more closely related to bird size than either dry-bulb temperature patterns or latitude. These relationships can be expressed numerically as regressions of mean wing length on either annual wet-bulb temperature or mean annual total heat per pound of air. Since increased evaporation at high altitudes and in arid areas accentuates the depression of a wet- bulb thermometer, my hypothesis may partially account for several cases of size variation in birds cited by others as disturbing exceptions to Bergmann's ecogeographic rule. Sections of a translation of Bergmann's paper published in 1847 are given. The biological mechanisms by which these relationships are maintained are unknown, and the wide range of tolerance by birds to diurnal and seasonal temperature variations tends to mask them. If the well-established inverse relationship between weight and metabolic rate per gram of homeotherms is operative on the intraspecific level, the relationships can be discussed in terms of avenues of heat loss and of energy budget equations.
21565667
Pleistocene climatic cycling drives intra‐specific diversification in the intermediate horseshoe bat (Rhinolophus affinis) in Southern China
The repeated formation and loss of land‐bridges during the Pleistocene have had lasting impacts on population genetic structure. In the tropics, where island populations persisted through multiple glacial cycles, alternating periods of isolation and contact are expected to have driven population and taxonomic divergence. Here, we combine mitochondrial and nuclear sequence data with microsatellites to dissect the impact of Pleistocene climate change on intra‐specific diversification in the horseshoe bat Rhinolophus affinis. This taxon shows considerable morphological and acoustic variation: two parapatric subspecies (himalayanus and macrurus) occur on mainland China and a third (hainanus) on Hainan Island. Our phylogeographic reconstruction and coalescent analyses suggest the island subspecies formed from an ancestral population of himalayanus via two colonization events c. 800 000 years before present. R. a. hainanus then recolonized the mainland, forming macrurus and thus a secondary contact zone with himalayanus. Finally, macrurus recolonized Hainan following the LGM. We found that all three biological events corresponded to known periods of land‐bridge formation. Evidence of introgression was detected between macrurus and both its sister taxa, with geographical proximity rather than length of separation appearing to be the biggest determinant of subsequent genetic exchange. Our study highlights the important role of climate‐mediated sea level changes have had in shaping current processes and patterns of population structure and taxonomic diversification.
85961368
Past potential habitats shed light on the biogeography of endemic tree species of the Western Ghats biodiversity hotspot, South India
Aim To investigate how Quaternary climatic changes affected the habitats that support endemic tree species distributions in a tropical rain forest. Based on past and present predicted species distributions, we assessed (1) whether climatic conditions may have supported species survival in the same area over the studied period, (2) the effect of ecological niche specialization on speciesspecific responses, and (3) the persistence of current populations in areas that were more climatically stable over time.
55313342
A brief overview of the Western Ghats - Sri Lanka biodiversity hotspot
The Western Ghats of India and Sri Lanka biodiversity hotspot is often regarded as one unit because of shared biogeographical history. However, recent studies suggest that certain faunal components, particularly in the wet zones are distinct. This article looks at the existing information on species richness and endemicity of taxa in both regions. Data are available on some taxa but not on others, and many taxa have not received equal attention in both regions. The natural ecosystems of this hotspot are under threat and urgent conservation action is needed, especially in augmenting the protected area network. There is also the need for increasing the level of scientific collaboration in biodiversity studies between the two countries.
3765183
Ancient Geographical Gaps and Paleo-Climate Shape the Phylogeography of an Endemic Bird in the Sky Islands of Southern India
Background Sky islands, formed by the highest reaches of mountain tracts physically isolated from one another, represent one of the biodiversity-rich regions of the world. Comparative studies of geographically isolated populations on such islands can provide valuable insights into the biogeography and evolution of species on these islands. The Western Ghats mountains of southern India form a sky island system, where the relationship between the island structure and the evolution of its species remains virtually unknown despite a few population genetic studies. Methods and Principal Findings We investigated how ancient geographic gaps and glacial cycles have partitioned genetic variation in modern populations of a threatened endemic bird, the White-bellied Shortwing Brachypteryx major, across the montane Shola forests on these islands and also inferred its evolutionary history. We used Bayesian and maximum likelihood-based phylogenetic and population-genetic analyses on data from three mitochondrial markers and one nuclear marker (totally 2594 bp) obtained from 33 White-bellied Shortwing individuals across five islands. Genetic differentiation between populations of the species correlated with the locations of deep valleys in the Western Ghats but not with geographical distance between these populations. All populations revealed demographic histories consistent with population founding and expansion during the Last Glacial Maximum. Given the level of genetic differentiation north and south of the Palghat Gap, we suggest that these populations be considered two different taxonomic species. Conclusions and Significance Our results show that the physiography and paleo-climate of this region historically resulted in multiple glacial refugia that may have subsequently driven the evolutionary history and current population structure of this bird. The first avian genetic study from this biodiversity hotspot, our results provide insights into processes that may have impacted the speciation and evolution of the endemic fauna of this region.
53144163
Singing in the sky: song variation in an endemic bird on the sky islands of southern India
Birdsong structure is known to vary across different scales of geographical separation, from differences between neighbours in a habitat to populations across continents. The high-elevation regions of the Western Ghats mountains in southern India form ‘sky islands’ containing the unique Shola habitat. Bird species on such sky islands are often specifically adapted to habitats typical of these islands while populations on different islands may have been geographically isolated over varying periods of time. Forest fragmentation can intensify the effects of such isolation by affecting species dispersal processes. We 
examined the effects of genetic differentiation across populations on the song of a threatened, endemic bird, the white-bellied shortwing, Brachypteryx major, on different islands of this sky island system. We compared songs from three populations, one of which on one island was genetically distinct from the other two populations on another island. These two populations were genetically similar but separated by recent deforestation. We recorded songs from 23 individuals and characterized 572 songs by 13 parameters. Multivariate analyses revealed significant differences in song between the three populations, with the genetically distinct populations across the two islands being the most differentiated. This was supported by a visual and aural examination of spectrograms that revealed characteristic qualitative differences in songs across these populations. Finally, this study corroborates accepted patterns of congruence between song and genetic divergence across islands and also highlights the difference in song between anthropogenically fragmented, but genetically similar populations, possibly owing to cultural drift. 2011 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
88645517
Geographical Variation of Rhinolophus affinis (Chiroptera: Rhinolophidae) in the Sundaic Subregion of Southeast Asia, including the Malay Peninsula, Borneo and Sumatra
Rhinolophus affinis sensu lato is a widespread bat species in South and Southeast Asia which shows considerable geographical variation in its morphology, echolocation call frequencies and genetics. The taxonomic status of the taxon in the Sundaic subregion remains uncertain however as the limited studies to date have been largely based on morphology. The aim of the present study was to determine the taxonomic status of subspecific forms recognized in the subregion and to evaluate phylogeographic distinctiveness between those occurring in Borneo and the Malay Peninsula using genetic, morphological and acoustic datasets. Two forms were confirmed: R. a. nesites from Borneo and R. a. superans from the peninsula. The previous recognition of a population from southernmost Sumatra as R. a. superans was not supported, however, as this form is likely R. a. affinis. Genetic divergence between these three forms is rather deep and is estimated to have occurred during the arid climatic period of the Pleistocene when suitable habitats were reduced to isolated pockets. Our results support the phylogeographic distinctiveness hypothesis as R. affinis sensu lato shows discrete affinities between Borneo and the Malay Peninsula. Discovery of new forms of R. affinis is likely with greater sampling effort throughout the region. Our study also demonstrates the importance of employing multiple datasets in taxonomic evaluations, as the use of morphological and/or acoustic datasets alone could lead to erroneous conclusions.
128421495
Relief and climate in South Asia: the influence of the western ghats on the current climate pattern of peninsular India
The 1500-km-long Western Ghats mountain barrier of peninsular India interacts with the southwest monsoon in a manner which bears heavily on the exceptionally varied climate pattern of the Deccan. Karnataka Province alone concentrates five of the six major climate types of the entire Indian Union. This review explores the interactions between atmospheric structure over South Asia and relief and discusses the efficiency with which the passive margin uplift, second only to the Himalayan barrier, acts as a climatic gatekeeper to the subcontinent. Particular attention is given to rainfall patterns and regimes. These are revealed by a variety of statistical classification and mapping techniques, and the analysis is guided by the steep environmental gradient observed on the immediate backslope of the Ghats, where annual totals can drop from 6000 to 600 mm in ca. 80 km. This is strongly reflected in the landform, soil, vegetation and cropping patterns and raises the question of the relationship between the uplift history of the mountain barrier at geological time-scales, the history of the South Asian monsoon circulation and the stability and diversity of the climatic pattern as seen today. The tightly arranged suite of bioclimatic regions also provides a unique geographical backdrop to the agricultural diversity of South India, rarely found on such a scale in other monsoon contexts of the Tropics. © 1997 The Royal Meteorological Society.
19094494
Glaciations, gradients, and geography: multiple drivers of diversification of bush frogs in the Western Ghats Escarpment
The historical processes underlying high diversity in tropical biodiversity hotspots like the Western Ghats of Peninsular India remain poorly understood. We sampled bush frogs on 13 massifs across the Western Ghats Escarpment and examined the relative influence of Quaternary glaciations, ecological gradients and geological processes on the spatial patterns of lineage and clade diversification. The results reveal a large in situ radiation (more than 60 lineages), exhibiting geographical structure and clade-level endemism, with two deeply divergent sister clades, North and South, highlighting the biogeographic significance of an ancient valley, the Palghat Gap. A majority of the bush frog sister lineages were isolated on adjacent massifs, and signatures of range stasis provide support for the dominance of geological processes in allopatric speciation. In situ diversification events within the montane zones (more than 1800 m) of the two highest massifs suggest a role for climate-mediated forest-grassland persistence. Independent transitions along elevational gradients among sub-clades during the Miocene point to diversification along the elevational gradient. The study highlights the evolutionary significance of massifs in the Western Ghats with the high elevations acting as centres of lineage diversification and the low- and mid-elevations of the southern regions, with deeply divergent lineages, serving as museums.
128737785
Effects of precipitation, temperature and topographic parameters on evergreen vegetation greenery in the Western Ghats, India
Bi-weekly National Oceanic and Atmospheric Administration-advanced very high-resolution radiometer (NOAA-AVHRR) satellite data covering a fourteen-year time period (1990–2003) were used to examine spatial patterns in the normalized difference vegetation index (NDVI) and their relationships with environmental variables covering tropical evergreen forests of the Western Ghats, India. NDVI values and corresponding environmental variables were extracted from 23 different forested sites using the NOAA-AVHRR global inventory monitoring and modelling studies (GIMMS) dataset. We specifically used the partial least square (PLS) multivariate regression technique that combines features from principal component analysis and multiple regression to link spatial patterns in NDVI with the environmental variables. PLS regression analysis suggested the two-component model to be the best model, explaining nearly 71% of the variance in the NDVI datasets with relatively good R2 value of 0.78 and a predicted R2 value of 0.74. The most important positive predictors for NDVI included Riva's continentality index, precipitation indicators summed over different quarters, average precipitation and elevation. Also, the results from PLS regression clearly suggested that bio-climatic indicators that relied only on precipitation parameters had much more positive influence than indicators that combined both temperature and precipitation together. These results highlight the climatic controls of vegetation vigor in evergreen forests and have implications for monitoring bio-spheric activity, developing prognostic phenology models and deriving land cover maps in the Western Ghats region of India. Copyright © 2008 Royal Meteorological Society
7292709
Sky island bird populations isolated by ancient genetic barriers are characterized by different song traits than those isolated by recent deforestation
Abstract Various mechanisms of isolation can structure populations and result in cultural and genetic differentiation. Similar to genetic markers, for songbirds, culturally transmitted sexual signals such as breeding song can be used as a measure of differentiation as songs can also be impacted by geographic isolation resulting in population‐level differences in song structure. Several studies have found differences in song structure either across ancient geographic barriers or across contemporary habitat barriers owing to deforestation. However, very few studies have examined the effect of both ancient barriers and recent deforestation in the same system. In this study, we examined the geographic variation in song structure across six populations of the White‐bellied Shortwing, a threatened and endemic songbird species complex found on isolated mountaintops or “sky islands” of the Western Ghats. While some sky islands in the system are isolated by ancient valleys, others are separated by deforestation. We examined 14 frequency and temporal spectral traits and two syntax traits from 835 songs of 38 individuals across the six populations. We identified three major song clusters based on a discriminant model of spectral traits, degree of similarity of syntax features, as well as responses of birds to opportunistic playback. However, some traits like complex vocal mechanisms (CVM), relating to the use of syrinxes, clearly differentiated both ancient and recently fragmented populations. We suggest that CVMs may have a cultural basis and can be used to identify culturally isolated populations that cannot be differentiated using genetic markers or commonly used frequency‐based song traits. Our results demonstrate the use of bird songs to reconstruct phylogenetic groups and impacts of habitat fragmentation even in complex scenarios of historic and contemporary isolation.
89319806
Climatic and geographic barriers drive distributional patterns of bird phenotypes within peninsular India
Modern phylogenetic data provide unparalleled ability to test biogeographic paradigms, often suggested by differences in species distribution patterns. However, such approaches have been applied less at regional scales, particularly in Asia. In the absence of such data, we examine if concordance of distributional patterns for phenotypes (subspecies) suggest potential biogeographic barriers for birds in peninsular India. Specifically, we examine climatic and physical factors that might limit phenotype distributions in this region.

Various physical, vegetation and climatic barriers were demarcated to identify potential biogeographic units within peninsular India. We then collated occurrence of endemic or disjunctly distributed species and subspecies within these units using published range maps. We also quantified turnover between potential units, allowing us to identify significant biogeographic barriers. Three time-step climate data (Last Glacial Maxima, mid-Holocene and present) enabled us to examine differences between these potential biogeographic regions through time.

The Palk Straits, followed by the Goa Gap (∼ 16°N) and the Godavari River emerged as the major barriers in this region. The Palk Straits and Godavari are physical barriers while Goa Gap appears to be a climate-mediated ecological divide. Mountain barriers like the Palghat Gap are not the most significant barriers as previously thought. Climatically intermediate regions appeared unstable in the past and showed inconsistent affinities to different geographic units across families. We suggest that relative climatic stability of the wet regions of the southern western Ghats could be responsible for high subspecies endemism here. Our approach provides hypotheses that can be tested with comparative multi-species phylogeographic data in the future.
130428894
A key to the bats (Mammalia: Chiroptera) of South Asia
A checklist and dichotomous key to 128 species of bats known from South Asia including Afghanistan, India, Pakistan, Nepal, Bhutan, Bangladesh, Sri Lanka and Maldives is provided. Character matrices for families, genera and species are also included. This article also briefly reviews their distribution (both physiographic and country-wise), status and main identification characters
55736033
Phenetic relationships among bats of the family Rhinolophidae
P h enetic analyses, u sin g the com m on-part-rem oved transform ation o f W ood (1983), w ere perform ed on 2.5 - 6.4% o f the variance th at describes m orphom etric differences am ong bats o f the fam ily R hinolophidae. Tw o ordination m ethods, one clustering tech ­ nique, and a m inim um -spanning tree were em ployed to assess patterns o f sim ilarity am ong 62 species. Tw o m ajor phenetic groups were revealed. One com prised O riental and A ustralian species, whereas the other contained E thiopian and P alaearctic taxa. On the basis o f m orphological sim ilarity, all b ut one species w ere provisionally a r­ ranged in 11 phenetic groups: m egaphyllus, rouxii, euryotis, pearsonii, philippinensis, trifoliaius, fum igatu s, ferrum equinum , capensis, euryale, and hipposideros. M ensural data w ere not su fficien t to clarify the status o f R. m aclaudi. B ased on the m or­ phological dispersion analysis, the Oriental region should be regarded as the center o f origin o f the fam ily. On the basis o f phylogenetic and functional factors, a close ancestor o f rhinolophids probably lived in tropical rain forests, flew slow ly em itting low -frequency sounds, and caught relatively soil b ut large prey.
55059252
Landscape scale habitat suitability modelling of bats in the Western Ghats of India: Bats like something in their tea
Abstract To conserve biodiversity it is imperative that we understand how different species respond to land use change, and determine the scales at which habitat changes affect species' persistence. We used habitat suitability models (HSMs) at spatial scales from 100–4000 m to address these concerns for bats in the Western Ghats of India, a biodiversity hotspot of global importance where the habitat requirements of bats are poorly understood. We used acoustic and capture data to build fine scale HSMs for ten species (Hesperoptenus tickelli, Miniopterus fuliginosus, Miniopterus pusillus, Myotis horsfieldii, Pipistrellus ceylonicus, Megaderma spasma, Hipposideros pomona, Rhinolophus beddomei, Rhinolophus indorouxii and Rhinolophus lepidus) in a tea-dominated landscape. Small (100–500 m) scale habitat variables (e.g. percentage tea plantation cover) and distances to habitat features (e.g. distance to water) were the strongest predictors of bat occurrence, likely due to their high mobility, which enables them to exploit even small or isolated foraging areas. Most species showed a positive response to coffee plantations grown under native shade and to forest fragments, but a negative response to more heavily modified tea plantations. Two species were never recorded in tea plantations. This is the first study of bats in tea plantations globally, and the first ecological Old World bat study to combine acoustic and capture data. Our results suggest that although bats respond negatively to tea plantations, tea-dominated landscapes that also contain forest fragments and shade coffee can nevertheless support many bat species.
25723401
Patterns and causes of geographic variation in bat echolocation pulses.
Evolutionary biologists have a long-standing interest in how acoustic signals in animals vary geographically, because divergent ecology and sensory perception play an important role in speciation. Geographic comparisons are valuable in determining the factors that influence divergence of acoustic signals. Bats are social mammals and they depend mainly on echolocation pulses to locate prey, to navigate and to communicate. Mounting evidence shows that geographic variation of bat echolocation pulses is common, with a mean 5-10 kHz differences in peak frequency, and a high level of individual variation may be nested in this geographical variation. However, understanding the geographic variation of echolocation pulses in bats is very difficult, because of differences in sample and statistical analysis techniques as well as the variety of factors shaping the vocal geographic evolution. Geographic differences in echolocation pulses of bats generally lack latitudinal, longitudinal and elevational patterns, and little is known about vocal dialects. Evidence is accumulating to support the fact that geographic variation in echolocation pulses of bats may be caused by genetic drift, cultural drift, ecological selection, sexual selection and social selection. Future studies could relate geographic differences in echolocation pulses to social adaptation, vocal learning strategies and patterns of dispersal. In addition, new statistical techniques and acoustic playback experiments may help to illustrate the causes and consequences of the geographic evolution of echolocation pulse in bats.
84698986
Do you hear what I hear? Implications of detector selection for acoustic monitoring of bats
Summary 
The probability of detecting the echolocation calls of bats is affected by the strength of the signal as well as the directionality and frequency response of the acoustic detectors. Regardless of the research question, it is important to quantify variation in recording system performance and its impacts on bat detection results. The purpose of this study was to compare the detection of echolocation calls among five commonly used bat detectors: AnaBat SD2 (Titley Scientific), Avisoft UltraSoundGate 116 CM16/CMPA (Avisoft Bioacoustics), Batcorder 2·0 (ecoObs), Batlogger (Elekon AG) and Song Meter SM2BAT (Wildlife Acoustics). 
We used playback of synthetic calls to optimize detection settings for each system. We then played synthetic signals at four frequencies (25, 55, 85 and 115 kHz) at 5-m intervals (5–40 m) and three angles (0°, 45°, 90°) from the detectors. Finally, we recorded free-flying bats (Lasiurus cinereus), comparing the number of calls detected by each detector. 
Detection was most affected by the frequency dominating the signal and the distance from the source. The effect of angle was less apparent. In the synthetic signal experiment, Avisoft and Batlogger outperformed other detectors, while Batcorder and Song Meter performed similarly. Batlogger performed better than the other detectors at angles off-centre (45° and 90°). AnaBat detected the fewest signals and none at 85 kHz or 115 kHz. Avisoft detected the most signals. In the free-flying bat experiment, Batlogger recorded 93% of calls relative to Avisoft, while AnaBat, Batcorder and Song Meter recorded 40–50% of the calls detected by Avisoft. 
Numerous factors contribute to variation in data sets from acoustic monitoring; our results demonstrate that choice of detector plays a role in this variation. Differences among detectors make it difficult to compare data sets obtained with different systems. Therefore, the choice of detector should be taken into account in designing studies and considering bat activity levels among studies using different detectors.
14953216
Response to Comment on “Methods to account for spatial autocorrelation in the analysis of species distributional data: a review”
I was amused to read, in a criticism of another publication, that the criticised authors did not adhere to the ‘‘principles of ecological niche modelling’’ (McNyset and Blackburn 2006, p. 782). There aren’t any such ‘‘principles’’. Ecological niche modelling really is statistics on species distribution data. All methods employed need to be statistically consistent, i.e. meet the assumptions made. (It would be a nice bonus if the analysis would also make ecological sense.) In the case discussed below, the crucial assumption is independence of data points, and it is usually violated in spatial distribution data, by spatial autocorrelation. Autologistic regression (Augustin et al. 1996), and its generalisation the autocovariate regression, has up to now been the most popular way to deal with spatial autocorrelation in biogeographical analysis of species distribution (Dormann 2007b). In two recent papers analysing simulated data, this method has, however, performed worse than other methods (Dormann 2007a, Dormann et al. 2007), calling into question the validity of its use. In a comment, Betts et al. (2009, this issue) warn that these conclusions may be incorrect, and that autocovariate regression can be used when applied and interpreted properly. In the following paragraphs, I like to draw attention to two issues relevant in this debate: the use of the word ‘‘space’’, and the ecological interpretation of the values of the autocovariate (and other measures of aggregation or separation from spatial models in general), i.e. what the data tell us about the species. I was seriously confused, when I realised that the autocovariate regression as applied in biogeography may be biased. In our review (Dormann et al. 2007), autocovariate regression was the only method that yielded a consistent bias in the parameter estimation, an observation confirmed by further simulations specifically looking at autologistic regression (Dormann 2007a). However, as Betts et al. pointed out correctly, all these analyses were carried out on the same underlying spatial structure, and if the environmental variable determining the virtual species’ distribution (called ‘‘rain’’) was confounded with its spatial aggregation (what Betts et al. termed ‘‘collinearity of environment with space’’), all these results may be fundamentally flawed. Since several previous studies have shown autologistic regression to be a reliable method (Wu and Huffer 1997, Huffer and Wu 1998, Hoeting et al. 2000, Hooten et al. 2003, Wintle and Bardos 2006), this explanation seems reasonable. So, why don’t I simply concede my error and let everyone use autocovariate regression in peace? There are several lines of argument that indicate that my results may not, after all, be wrong. A brief list: 1) environment and ‘‘space’’ are not correlated, unless we accept Betts et al.’s definition of ‘‘space’’. 2) Confirmation for the method comes only from studies that use an iterative implementation and missing data (see the studies cited above). 3) The idea of the autocovariate has an intrinsic circularity (since the new explanatory variable is constructed from the data to be explained: Dormann 2007a). 4) Two other methods using variables to represent spatial effects in a somewhat comparable way to the autocovariate are unbiased under the simulated conditions (spatial eigenvector mapping SEVM: Griffith and Peres-Neto 2006, Dormann et al. 2007, and a new wavelet method: Carl and Kuhn 2007, Carl et al. 2008). Here, I shall only address the first topic, which I regard as most important to the differences between my view and that of Betts et al. (2009). Spatial models attempt to correct for the non-independence of data points near each other, which may be connected through ecological and non-ecological processes (yielding spatial autocorrelation). To do so, they usually work through some quantification of spatial distances between sites (even if the model formula uses locations, i.e. longitude and latitude as inputs). Location, as one might have naively suspected, is thus not the same as ‘‘space’’ in the sense of spatial models. To avoid confusion, I prefer to use ‘‘neighbourhood’’ instead of ‘‘space’’ to refer to distance-related influences, irrespective of their location. The effect of a point’s neighbourhood on this point can thus be referred to as the effect of ‘‘space’’ (in the words of Betts et al.) or of the neighbourhood. How can this be Ecography 32: 379 381, 2009 doi: 10.1111/j.1600-0587.2009.05907.x # 2009 The Author. Journal compilation # 2009 Ecography
62229412
Model selection and multimodel inference : a practical information-theoretic approach
The second edition of this book is unique in that it focuses on methods for making formal statistical inference from all the models in an a priori set (Multi-Model Inference). A philosophy is presented for model-based data analysis and a general strategy outlined for the analysis of empirical data. The book invites increased attention on a priori science hypotheses and modeling. Kullback-Leibler Information represents a fundamental quantity in science and is Hirotugu Akaike's basis for model selection. The maximized log-likelihood function can be bias-corrected as an estimator of expected, relative Kullback-Leibler information. This leads to Akaike's Information Criterion (AIC) and various extensions. These methods are relatively simple and easy to use in practice, but based on deep statistical theory. The information theoretic approaches provide a unified and rigorous theory, an extension of likelihood theory, an important application of information theory, and are objective and practical to employ across a very wide class of empirical problems. The book presents several new ways to incorporate model selection uncertainty into parameter estimates and estimates of precision. An array of challenging examples is given to illustrate various technical issues. This is an applied book written primarily for biologists and statisticians wanting to make inferences from multiple models and is suitable as a graduate text or as a reference for professional analysts.
61558924
The ecodist Package for Dissimilarity-based Analysis of Ecological Data
Ecologists are concerned with the relationships between species composition and environmental framework incorporating space explicitly is an extremely flexible tool for answering these questions. The R package ecodist brings together methods for working with dissimilarities, including some not available in other R packages. We present some of the features of ecodist, particularly simple and partial Mantel tests, and make recommendations for their effective use. Although the partial Mantel test is often used to account for the effects of space, the assumption of linearity greatly reduces its effectiveness for complex spatial patterns. We introduce a modification of the Mantel correlogram designed to overcome this restriction and allow consideration of complex nonlinear structures. This extension of the method allows the use of partial multivariate correlograms and tests of relationship between variables at different spatial scales. Some of the possibilities are demonstrated using both artificial data and data from an ongoing study of plant community composition in grazinglands of the northeastern United States.
36081334
ECHOLOCATION CALL FREQUENCY DIFFERENCES BETWEEN GEOGRAPHIC ISOLATES OF RHINONICTERIS AURANTIA (CHIROPTERA: HIPPOSIDERIDAE): IMPLICATIONS OF NASAL CHAMBER SIZE
Abstract Most previous studies considering intraspecific differences in bat echolocation call frequency among geographic groups have related this to morphological features not directly involved in producing the characteristics of the emitted signal. We related a pattern of intraspecific call differences to the size of nasal chambers (estimated from radiographs of museum specimens), expecting chamber dimensions to be functionally coupled with the sound source. Such a relationship is potentially informative in the context of competing hypotheses that account for call frequency differences. Allopatry has been a precursor to differences in echolocation call frequency between isolated populations of the Australian endemic orange leaf-nosed bat (Rhinonicteris aurantia (Gray, 1845); Pilbara isolate: 120.99 ± 1.91 kHz; compared with Kimberley region: 114.65 ± 1.98 kHz and Northern Territory: 114.62 ± 2.10 kHz). Correlations with morphological features not directly involved in signal production or modification were either moderate (nose-leaf width) or absent (forearm length). Overall nasal volume was shown to be relatively smaller in the Pilbara population, which had higher average call frequency. This relationship was expected given the suggested function of nasal chambers in impedance matching. The finding is significant because nasal chamber size was the only character observed to vary in a species that was otherwise conserved morphologically, suggesting adaptation and not a simple scaling relationship with body size that might be more indicative of drift. We consider that the combination of patterns from echolocation call frequency and associated morphological features, as well as neutral DNA markers, provide adequate support for recognition of the separate populations of R. aurantia for conservation, according to more recent concepts that consider ecological as well as genetic characters when allocating groups to evolutionarily significant units.
83593660
The allometry of echolocation call frequencies in horseshoe bats: nasal capsule and pinna size are the better predictors than forearm length
The evolution of acoustic signals and the morphological traits mediating its production and reception are often coupled. The echolocation call frequencies of horseshoe bats normally decline as body size increases, but remarkable exceptions to the rule have been observed, such as Rhinolophus macrotis, R. marshalli and R. rex, having lower echolocation call frequencies than expected for their body size. Forearm length is commonly used to scale allometric relationships across horseshoe bats. However, little is known about the allometric relationships between echolocation call frequencies and morphological traits mediating directly echolocation calls' production or reception, such as the nasal capsule, the cochlea or the pinna. Here we have tested the allometry hypothesis regarding the evolution of echolocation in 12 horseshoe bats distributed in China by integrating echolocation call frequencies, phylogeny, forearm length, cochlea size, pinna size and nasal capsule size. Our results showed no significant correlation between echolocation call frequency and forearm length across these species without considering the phylogeny of the group. However, ear length, ear width and nasal capsule size were significantly and negatively correlated with echolocation call frequencies among the studied species. The fit between the linear regression model and the data was much better for the relationships between echolocation call frequencies and pinna or nasal capsule size than for the relationship between echolocation call frequencies and forearm length. These findings illustrated that both pinna and nasal capsule size were better predictors of echolocation call frequencies than forearm length. Given that the echolocation call frequencies of horseshoe bats can play key roles in sexual selection and speciation, the divergence we observed among species may influence the evolution of echolocation calls across horseshoe bats in China.
140702156
Late Miocene-Pleistocene aridification of Asian inland revealed by geochemical records of lacustrine-fan delta sediments from the western Tarim Basin, NW China
Abstract Continuous Cenozoic deposits have accumulated in the Tarim Basin, northwestern China, and are crucial to investigating the aridification history of the Asian interior, which has long been thought to be linked with the growth of the Tibetan Plateau, retreat of the Para-Tethys Sea and global cooling. However, less and poor climatic records from the region hinder our understanding of the questions above. Here we report continuous lithologic (sedimentary color) and geochemical (CaCO3 and salt ions) records from precisely dated late Miocene–early Pleistocene sedimentary sequence from western Tarim Basin, NW China. They indicate that arid climate had prevailed within the basin at latest at ca. 5.7 Ma and gradually increased in degree until ca. 3.7 Ma. Between ca. 3.7 and 2.1 Ma, a hydrologic event occurred, which supplied more water from the Tien Shan. After ca. 2.1 Ma the climate in the basin turned to hyper arid. We attribute the stepwise drying of the Asian inland since ca. 5.7 Ma to the late Miocene–Pliocene episodic uplift of the Tibetan Plateau, Pamir and the Tien Shan and the connection of the Pamir with the Tien Shan in remote response to the collision of India with Asia.
87098055
The role of wet‐zone fragmentation in shaping biodiversity patterns in peninsular India: insights from the caecilian amphibian Gegeneophis
Aim Indian biodiversity is concentrated in the wet zone, which is disjunctly distributed in the north-east and in the peninsular Western and Eastern Ghats. The Eastern Ghats region is smaller and less well explored biologically and the affinities and origins of its biota poorly understood. Our aim was to assess whether divergence between east and west lineages might have been caused by fragmentation of the wet zone during Pleistocene climatic fluctuations, by Late Miocene wet-zone contraction or by more ancient events. We present the first dated phylogenetic test of these alternatives by inferring relationships and dating divergences within a wet-zone-restricted lineage endemic to the Eastern and Western Ghats. Location The Eastern and Western Ghats regions of peninsular India. Methods Molecular genetic data (one nuclear and four mitochondrial genes) were newly generated for the only known Eastern Ghats teresomatan caecilian amphibian (Gegeneophis orientalis) and the only Western Ghats congener (G. pareshi) for which molecular data were not previously available. Phylogenetic relationships were inferred for Indian indotyphlids using maximum likelihood and Bayesian inference methods. Divergence times within the inferred phylogeny were estimated using a Bayesian relaxed clock method, with the Seychelles versus Indian indotyphlid divergence calibrated based on the geological separation of their respective continental land masses. Results The single Eastern Ghats species of Gegeneophis is sister to all other (Western Ghats) Gegeneophis. The basalmost (and east-west) split within Gegeneophis likely occurred >35 Ma. Main conclusions Divergence between Eastern and Western Ghats Gegeneophis is too ancient to have been caused by wet-zone contraction in the Miocene or by Pleistocene climatic fluctuations. Our results are consistent with a relatively ancient origin of wet-zone lineages in the Eastern Ghats and a lack of gene flow between Eastern and Western Ghats Gegeneophis for tens of millions of years.
8820533
Differential introgression among loci across a hybrid zone of the intermediate horseshoe bat (Rhinolophus affinis)
BackgroundHybrid zones formed by the secondary contact of divergent lineages represent natural laboratories for studying the genetic basis of speciation. Here we tested for patterns of differential introgression among three X-linked and 11 autosomal regions to identify candidate loci related to either reproductive isolation or adaptive introgression across a hybrid zone between two Chinese mainland subspecies of the intermediate horseshoe bat Rhinolophus affinis: R. a. himalayanus and R. a. macrurus.ResultsOur results support the previous suggestion that macrurus formed when a third subspecies (R. a. hainanus) recolonized the mainland from Hainan Island, and that himalayanus is the ancestral taxon. However, this overall evolutionary history was not reflected in all loci examined, with considerable locus-wise heterogeneity seen in gene tree topologies, levels of polymorphism, genetic differentiation and rates of introgression. Coalescent simulations suggested levels of lineage mixing seen at some nuclear loci might result from incomplete lineage sorting. Isolation with migration models supported evidence of gene flow across the hybrid zone at one intronic marker of the hearing gene Prestin.ConclusionsWe suggest that phylogenetic discordance with respect to the species tree seen here is likely to arise via a combination of incomplete lineage sorting and a low incidence of introgression although we cannot rule out other explanations such as selection and recombination. Two X-linked loci and one autosomal locus were identified as candidate regions related to reproductive isolation across the hybrid zone. Our work highlights the importance of including multiple genomic regions in characterizing patterns of divergence and gene flow across a hybrid zone.
4631309
The complex evolutionary history of big-eared horseshoe bats (Rhinolophus macrotis complex): insights from genetic, morphological and acoustic data
Palaeoclimatic oscillations and different landscapes frequently result in complex population-level structure or the evolution of cryptic species. Elucidating the potential mechanisms is vital to understanding speciation events. However, such complex evolutionary patterns have rarely been reported in bats. In China, the Rhinolophus macrotis complex contains a large form and a small form, suggesting the existence of a cryptic bat species. Our field surveys found these two sibling species have a continuous and widespread distribution with partial sympatry. However, their evolutionary history has received little attention. Here, we used extensive sampling, morphological and acoustic data, as well as different genetic markers to investigate their evolutionary history. Genetic analyses revealed discordance between the mitochondrial and nuclear data. Mitochondrial data identified three reciprocally monophyletic lineages: one representing all small forms from Southwest China, and the other two containing all large forms from Central and Southeast China, respectively. The large form showed paraphyly with respect to the small form. However, clustering analyses of microsatellite and Chd1 gene sequences support two divergent clusters separating the large form and the small form. Moreover, morphological and acoustic analyses were consistent with nuclear data. This unusual pattern in the R. macrotis complex might be accounted for by palaeoclimatic oscillations, shared ancestral polymorphism and/or interspecific hybridization.
124258099
Monsoon circulation interaction with Western Ghats orography under changing climate
In this study, the authors have investigated the likely future changes in the summer monsoon over the Western Ghats (WG) orographic region of India in response to global warming, using time-slice simulations of an ultra high-resolution global climate model and climate datasets of recent past. The model with approximately 20-km mesh horizontal resolution resolves orographic features on finer spatial scales leading to a quasi-realistic simulation of the spatial distribution of the present-day summer monsoon rainfall over India and trends in monsoon rainfall over the west coast of India. As a result, a higher degree of confidence appears to emerge in many aspects of the 20-km model simulation, and therefore, we can have better confidence in the validity of the model prediction of future changes in the climate over WG mountains. Our analysis suggests that the summer mean rainfall and the vertical velocities over the orographic regions of Western Ghats have significantly weakened during the recent past and the model simulates these features realistically in the present-day climate simulation. Under future climate scenario, by the end of the twenty-first century, the model projects reduced orographic precipitation over the narrow Western Ghats south of 16°N that is found to be associated with drastic reduction in the southwesterly winds and moisture transport into the region, weakening of the summer mean meridional circulation and diminished vertical velocities. We show that this is due to larger upper tropospheric warming relative to the surface and lower levels, which decreases the lapse rate causing an increase in vertical moist static stability (which in turn inhibits vertical ascent) in response to global warming. Increased stability that weakens vertical velocities leads to reduction in large-scale precipitation which is found to be the major contributor to summer mean rainfall over WG orographic region. This is further corroborated by a significant decrease in the frequency of moderate-to-heavy rainfall days over WG which is a typical manifestation of the decrease in large-scale precipitation over this region. Thus, the drastic reduction of vertical ascent and weakening of circulation due to ‘upper tropospheric warming effect’ predominates over the ‘moisture build-up effect’ in reducing the rainfall over this narrow orographic region. This analysis illustrates that monsoon rainfall over mountainous regions is strongly controlled by processes and parameterized physics which need to be resolved with adequately high resolution for accurate assessment of local and regional-scale climate change.
31515108
Is food resource partitioning responsible for deviation of echolocation call frequencies from allometry in Rhinolophus macrotis?
There is an apparent allometric relationship between peak frequency of echolocation and body size in rhinophilids. However, some rhinolophids deviate from this rule. To date this variation has been explained as a result of partitioning of communication channels. An alternative hypothesis that food resource partitioning results in this divergence in expected frequencies was tested by comparing prey selection between Rhinolophus macrotis Blyth, 1844 and Rhinolophus lepidus Blyth, 1844 in Yunnan Province, China. These two sympatric species are morphologically similar but acoustically divergent: R. macrotis has an echolocation frequency significantly lower than that predicted by the allometric relationship, whereas that of R. lepidus agreed with expectations. Prey selection experiments, conducted in a flight tent, indicated that the dominant prey taxa of R. macrotis were Lasiocampidae, Arctiidae and Noctuidae, whilst that of R. lepidus were Arctiidae, Noctuidae and Ichneumonidae. R. macrotis ate more earless moths and fewer eared moths than R. lepidus, and R. macrotis fed on larger prey in general and captured a wider size range than that captured by R. lepidus. These results confirmed the existence of finely tuned trophic niche differentiation and suggested that food resource partitioning is one of the factors leading to lower peak frequency of calls in R. macrotis.
38756666
Ecomorphology, differentiated habitat use, and nocturnal activities of Rhinolophus and Hipposideros species in East Asian tropical forests.
We investigated the wing morphology and foraging distributions of sympatric Rhinolophus and Hipposideros species by acoustic sampling, measuring wing parameters, and observing bats in different settings of tropical East Asian forests, to evaluate their flexibility in habitat use and edge sensitivity. R. formosae and H. terasensis were more abundant at edges/in open habitats and shared the highest overlap, with R. formosae displaying the greatest breadth in habitat use, whereas R. monoceros had a higher abundance and feeding efficiency in forest interiors with a continuous canopy. H. terasensis was significantly larger and had higher wing loading and aspect ratio than R. formosae and R. monoceros, while R. formosae had higher wing loading but a lower aspect ratio than the smaller-sized R. monoceros. Shrubs and herbs were higher at sites where bats were captured than at those without bat captures, and R. monoceros and R. formosae were associated with greater canopy and ground coverage, respectively. R. monoceros always foraged while flying at lower heights close to the herb/shrub layers, while H. terasensis and R. formosae used perching to different extents, with R. formosae preferably using fly-catching techniques and appearing farther from the path in open forests rather than in forest interiors. Our results indicate that differences in wing parameters account for the different degrees of flexibility in habitat use, yet the deviations of call frequency from the expected values in R. formosae and H. terasensis suggest additional adaptations accounting for their flexibility in exploring habitats.
86851637
Assortative roosting in the two phonic types of Pipistrellus pipistrellus during the mating season
The European pipistrelle, Pipistrellus pipistrellus, consists of two phonic types that echolocate with frequencies of maximum energy (FMAXE) averaging 46 kHz and 55 kHz (named the 45 kHz and 55 kHz phonic types for simplicity). These two phonic types occur in sympatry over much of Britain. Between 1993 and 1995 mating groups of P. pipistrellus were located in bat boxes between August and October, the main mating period for these bats. Mating groups comprised a single male and up to three females. Broad-band, time-expanded recordings of search-phase echolocation calls were made from bats immediately after release. The average FMAXE of each bat was calculated: bats with an FMAXE less than 49 kHz were classed as 45 kHz phonic types and bats with an FMAXE greater than 52 kHz were classed as 55 kHz phonic types. A total of 16, 45 kHz groups and ten 55 kHz groups were located. No mating group ever contained more than one phonic type, although both types were known to be present at several of the study sites. Males emitted calls of higher frequency than females for both phonic types. The study suggests that the two phonic types are reproductively isolated and supports the hypothesis that P. pipistrellus should be considered as two cryptic sibling species.
85898573
Conservation value of forest fragments to Palaeotropical bats
Forested landscapes in Southeast Asia are becoming increasingly fragmented, making this region a conservation and research priority. Despite its importance, few empirical studies of effects of fragmentation on biodiversity have been undertaken in the region, limiting our ability to inform land-use regimes at a time of increased pressure on forests. We estimated the biodiversity value of forest fragments in peninsular Malaysia by studying fragmentation impacts on insectivorous bat species that vary in dependence of forest. We sampled bats at seven continuous forest sites and 27 forest fragments, and tested the influence of fragment isolation and area on the abundance, species richness, diversity, composition and nestedness of assemblages, and the abundance of the ten most common species. Overall, isolation was a poor predictor of these variables. Conversely, forest area was positively related with abundance and species richness of cavity/foliage-roosting bats, but not for that of cave-roosting or edge/open space foraging species. The smallest of fragments ( 300 ha contribute substantially to landscape-level bat diversity, and that small fragments also have some value. However, large tracts are needed to support rare, forest specialist species and should be the conservation priority in landscape-level planning. Species that roost in tree cavities or foliage may be more vulnerable to habitat fragmentation than those that roost in caves.