23430024
Widespread occurrence of a domestic dog mitochondrial DNA haplotype in southeastern US coyotes
Sequence analysis of the mitochondrial DNA control region from 112 southeastern US coyotes (Canis latrans) revealed 12 individuals with a haplotype closely related to those in domestic dogs. Phylogenetic analyses grouped this new haplotype in the dog/grey wolf (Canis familiaris/Canis lupus) clade with 98% bootstrap support. These results demonstrate that a male coyote hybridized with a female dog, and female hybrid offspring successfully integrated into the coyote population. The widespread distribution of this haplotype from Florida to West Virginia suggests that the hybridization event occurred long ago before the southeastern USA was colonized by coyotes. However, it could have occurred in the southeastern USA before the main front of coyotes arrived in the area between male coyotes released for sport and a local domestic dog. The introgression of domestic dog genes into the southeastern coyote population does not appear to have substantially affected the coyote's genetic, morphological, or behavioural integrity. However, our results suggest that, contrary to previous reports, hybridization can occur between domestic and wild canids, even when the latter is relatively abundant. Therefore, hybridization may be a greater threat to the persistence of wild canid populations than previously thought.
32450293
The problems with hybrids: setting conservation guidelines
Abstract Rates of hybridization and introgression are increasing dramatically worldwide because of translocations of organisms and habitat modifications by humans. Hybridization has contributed to the extinction of many species through direct and indirect means. However, recent studies have found that natural hybridization has played an important role in the evolution of many plant and animal taxa. Determining whether hybridization is natural or anthropogenic is crucial for conservation, but is often difficult to achieve. Controversy has surrounded the setting of appropriate conservation policies to deal with hybridization and introgression. Any policy that deals with hybrids must be flexible and must recognize that nearly every situation involving hybridization is different enough that general rules are not likely to be effective. We provide a categorization of hybridization to help guide management decisions
85690600
Analysis of Hybrid Zones
Hybrid zones are, roughly speaking, narrow regions in which genetically distinct populations meet, mate, and produce hybrids. They are often only a few hundred meters wide and yet may be several hundred kilometers long. They are found in a wide variety of organisms: Tables 1 and 2 list about 150 reasonably clear examples, in which there is a spatial transition between two hybridizing forms. Such a widespread and striking phenomenon requires explanation; more importantly, it offers us several ways of understanding the nature and origin of species. First, hybrid zones pose interesting questions for the taxonomist, for they contrast two views of the species: as a set of populations delimited by genetic barriers to gene exchange; and as a set of populations maintained in a particular stable equilibrium by selection. Second, the wide range of genotypes found in a hybrid zone can be used to analyze the genetic differences and selective forces that separate the taxa involved. This may allow some inferences about the way these differences evolved and, by extrapolation, about the way fully isolated species diverge from each other. Finally, models of parapatric speciation, and of Wright's "shifting balance," involve the formation, move­ ment, and modification of hybrid zones. Hybrid zones must be understood before the plausibility of these models can be judged. After clarifying our terminology, we will summarize the relevant theory and then see how this can be used to make inferences from field data. A notable increase in the number of detailed genetic studies of hybrid zones occurred over
86827967
Extinction by hybridization and introgression
▪ Abstract Nonindigenous species can bring about a form of extinction of native flora and fauna by hybridization and introgression either through purposeful introduction by humans or through habitat modification, bringing previously isolated species into contact. These phenomena can be especially problematic for rare species coming into contact with more abundant ones. Increased use of molecular techniques focuses attention on the extent of this underappreciated problem that is not always apparent from morphological observations alone. Some degree of gene flow is a normal, evolutionarily constructive process, and all constellations of genes and genotypes cannot be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species' existence.
53629605
Genetic divergence among populations of the Hawaiian duck, laysan duck, and mallard
Allozymic variation at 20 gene loci was estimated for populations of the Laysan Duck (Anas laysanensis) and the Hawaiian Duck (A. wyvilliana) from the Hawaiian archipelago, as well as for Mallard populations (A. platyrhynchos) from Hawaii and North America. The Laysan Duck and Hawaiian Duck are endemic, have experienced severe bottlenecks, and are listed as endangered species. Alternative alleles are fixed at six loci for Mallards versus Hawaiian anatids (Hawaiian and Laysan ducks). In contrast, every allelic variant found in the Laysan Duck was present in the Hawaiian Duck (but not vice versa), suggesting the former is an offshoot of the latter. The genetic distance (Nei's D) between Laysan and Hawaiian ducks is less than 0.01, while that between both Hawaiian and Laysan ducks and Mallards is greater than 0.45. The allozymic evidence also suggests that there has been extensive hy- bridization between Mallards and Hawaiian Ducks on Oahu, with the near disappearance of Hawaiian Duck alleles. However, there is only slight evidence of Mallard genic introgression into the Hawaiian Duck population on Kauai. Finally, the allozymic data suggest that the Hawaiian Duck is a distinct species from the Mallard, but that little genetic divergence has occurred between Hawaiian and Laysan ducks. Received 25 July 1991, accepted 8 March 1992.
85878110
Hybridization in the Catalina Island Mountain Mahogany (Cercocarpus traskiae): RAPD Evidence
The Catalina Island mountain mahogany is one of 10 species of shrubs and small trees (Lis 1992) comprising the genus Cercocarpus H. B. K (Rosaceae). Species in the genus are widely distributed throughout western North America and are delimited primarily on the basis of leaf characteristics (Mortenson 1973; Lis 1992). The Catalina Island mountain mahogany (C. traskiae Eastwood) is one of the most distinctive species in the genus due to its thick, coriaceous leaves and woolly pubescence on the leaf undersurface. The species is extremely rare, restricted to Wild Boar Gully on the southwest side of Santa Catalina Island in the Channel Islands off the coast of California (Fig. 1). When the population was first discovered in 1897, it consisted of over 40 individuals (Thorne 1967). Due to overgrazing by introduced mammalian herbivores (Coblentz 1980; Hobbs 1980), however, the population has been greatly reduced (Rieseberg et al. 1989). Cercocarpus traskiae is listed as endangered by the state of California and thus is afforded protection by California law (Smith & Berg 1988). Inexplicably, the species is not listed as endangered or threatened by the U.S. Fish and Wildlife Service, although it is under consideration for listing. In the late 1970s a detailed inventory of the Wild Boar Gully population was undertaken, and a total of eight Cercocarpus trees were discovered and tagged (Martin 1984). In addition, two of the trees (A, B; Fig. 1) were fenced to protect them from herbivores, and in 1985 the Catalina Conservancy constructed a larger fence around an area that included both trees, as well as about an acre of good habitat. The fencing effort was extremely successful, and by 1988 approximately 70 seedlings were observed within the fenced area (Rieseberg et al. 1989). Unfortunately, several of the adult plants resembled the island mountain mahogany, Cercocarpus betuloides Torrey & A. Gray var. blancbeae (C. Schneider) Little, in key morphological features such as leaf pubescence and leaf thickness or were immediate for these characters (descriptions of both species are given by R. Lis in Hickman [1993]). Cercocarpus betuloides var. blancbeae is only slightly more widespread than C traskiae, occurring on all of the Channel Islands except San Clemente. But the species is much more abundant than C traskiae on Santa Catalina and is known to occur in adjacent canyons, so the possibility of hybridization between the two species could not be dismissed. Furthermore, it is suspected that some of the seedlings might be of hybrid origin (T. Martin, personal communication). In an attempt to clarify the identity of morphologically ambiguous individuals, Rieseberg et al. (1989) undertook a study of allozymic variation and leaf anatomy of all the adult mahogany trees discovered in Wild Boar Gully. Of the eight adult trees in the Gully, three were anatomically intermediate between C. traskiae and C betuloides var. blancbeae, suggestive of hybridization. Analysis of 17 isozyme loci in C traskiae, as well as a nearby population of C betuloides var. blancbeae (Fig. 1), revealed one diagnostic isozyme polymorphism differentiating the two species. Based on this single isozyme polymorphism, five of the eight trees were diagnosed as C traskiae, one as C betuloides var. blancbeae, and two as hybrids. However, isozyme analyses of the 28 seedlings large enough to survive the loss of a single leaf revealed all to be "pure" C traskiae. The results from this study were not entirely satisfactory, however, because the classification of individuals as parental versus hybrid was based on a single locus. The use of a single diagnostic locus can ensure the correct identification of first-generation hybrids, but F2or later-generation hybrid or backcross progeny could easily be misdiagnosed as belonging to one of the parental classes. Thus, it was not surprising that two of the plants lacking a hybrid enzyme genotype were anatomically Paper submitted April 1994; revised manuscript accepted July 15, 1994.
83868119
Molecular Genetics of Pre‐1940 Red Wolves
Conservation of the endangered red wolf (Canis rufus) has become a controversial issue because its genetic and morphological composition has been altered by hybridization with coyotes (C. latrans) and possibly gray wolves (C. lupus) making its evolutionary origins difficult to ascertain. The evolutionary hypothesis based on morphological data is that the red wolf had an Early Pleistocene origin and was the predecessor of both modern coyotes and gray wolves. After 1940 red wolves hybridized with coyotes as the species vanished from the wild. In contrast to this ancient origin-recent introgression hypothesis, molecular data are more consistent with an origin through hybridization between gray wolves and coyotes. Interspecific hybridization may have occurred repeatedly over time prior to European settlement in the southcentral United States or may have been induced recently by anthropogenic changes. We review recent molecular evidence and present new results from the analysis of mitochondrial and nuclear DNA markers in pre-1940 populations of red wolves. Our results are inconsistent with an ancient origin of the red wolf and support the hybridization model. We discuss possible hybridization scenarios and reasons for the red wolf reintroduction program to be concerned with the effects of genetic introgression from coyotes.
25976335
Molecular genetics of the most endangered canid: the Ethiopian wolf Canis simensis
The world's most endangered canid is the Ethiopian wolf Canis simensis, which is found in six isolated areas of the Ethiopian highlands with a total population of no more than 500 individuals. Ethiopian wolf populations are declining due to habitat loss and extermination by humans. Moreover, in at least one population, Ethiopian wolves are sympatric with domestic dogs, which may hybridize with them, compete for food, and act as disease vectors. Using molecular techniques, we address four questions concerning Ethiopian wolves that have conservation implications. First, we determine the relationships of Ethiopian wolves to other wolf‐like canids by phylogenetic analysis of 2001 base pairs of mitochondrial DNA (mtDNA) sequence. Our results suggest that the Ethiopian wolf is a distinct species more closely related to gray wolves and coyotes than to any African canid. The mtDNA sequence similarity with gray wolves implies that the Ethiopian wolf may hybridize with domestic dogs, a recent derivative of the gray wolf. We examine this possibility through mtDNA restriction fragment analysis and analysis of nine microsatellite loci in populations of Ethiopian wolves. The results imply that hybridization has occurred between female Ethiopian wolves and male domestic dogs in one population. Finally, we assess levels of variability within and between two Ethiopian wolf populations. Although these closely situated populations are not differentiated, the level of variability in both is low, suggesting long‐term effective population sizes of less than a few hundred individuals. We recommend immediate captive breeding of Ethiopian wolves to protect their gene pool from dilution and further loss of genetic variability.
16384973
Patterns of differentiation and hybridization in North American wolflike canids, revealed by analysis of microsatellite loci.
Genetic divergence and gene flow among closely related populations are difficult to measure because mutation rates of most nuclear loci are so low that new mutations have not had sufficient time to appear and become fixed. Microsatellite loci are repeat arrays of simple sequences that have high mutation rates and are abundant in the eukaryotic genome. Large population samples can be screened for variation by using the polymerase chain reaction and polyacrylamide gel electrophoresis to separate alleles. We analyzed 10 microsatellite loci to quantify genetic differentiation and hybridization in three species of North American wolflike canids. We expected to find a pattern of genetic differentiation by distance to exist among wolflike canid populations, because of the finite dispersal distances of individuals. Moreover, we predicted that, because wolflike canids are highly mobile, hybrid zones may be more extensive and show substantial changes in allele frequency, relative to nonhybridizing populations. We demonstrate that wolves and coyotes do not show a pattern of genetic differentiation by distance. Genetic subdivision in coyotes, as measured by theta and Gst, is not significantly different from zero, reflecting persistent gene flow among newly established populations. However, gray wolves show significant subdivision that may be either due to drift in past Ice Age refugia populations or a result of other causes. Finally, in areas where gray wolves and coyotes hybridize, allele frequencies of gray wolves are affected, but those of coyotes are not. Past hybridization between the two species in the south-central United States may account for the origin of the red wolf.
85011290
Hybridization between Wolves and Dogs
Concern has been expressed that European populations of gray wolves (Canis lupus) have extensively hybridized with domestic dogs (C. familiaris). We reviewed and analyzed surveys of mitochondrial and biparentally inherited genetic markers in dogs and wild populations of wolf-like canids. Although dog-wolf hybrids have been observed in the wild, significant introgression of dog markers into wild wolf populations has not yet occurred. Our investigation suggests that hybridization may not be an important conservation concern even in small, endangered wolf populations near human settlements. The behavioral and physiological differences between domestic dogs and gray wolves may be sufficiently great such that mating is unlikely and hybrid offspring rarely survive to reproduce in the wild.
32688925
A study of dog-coyote hybrids and implications concerning hybridization in canis.
A female, mongrel, black and white, 25-pound terrier dog bred to a captive male Kansas coyote gave birth on 20 April 1954 to six F1 hybrid “coy-dogs” From 1956 through 1961 these produced four litters of F2 hybrids. Five of the F1 generation resembled melanistic, short-legged coyotes; the sixth was similarly colored but shaggy like the mother. The F2 generation was more varied, dog-like to somewhat coyote-like animals.

Behavior varied, but all of the animals were intermediate, with some coyote-like traits, including howling. They were aggressive among themselves and had a dominance hierarchy in males and probably in females, with males dominating females. They displayed no submissive behavior adequate to inhibit a dominant individual from attacking an inferior. No trace of male parental care (which is strong in coyotes and absent in dogs) was noted in the coy-dogs.

The generally small size of the F2 litters (mean 2.25, range 1 to 3) and their small number in relation to the possible number, suggests some decrease in fecundity but might also have resulted from crowding or other suboptimal conditions inducing prenatal mortality. There was a rather high incidence of dental anomaly among the hybrids.

Both sexes of the hybrids, as in the comparatively few comparable studies, displayed a late autumnal, annual mating season (in this case in December), differing from that of coyotes, which breed in late winter (mainly February). The literature of dog-coyote hybridism is summarized and the implications of the peculiar reproductive timing of hybrids are discussed with respect to the possibility of hybridization in the wild leading (a) to the establishment of hybridswarms of coy-dogs and intermediate individuals; (b) to the introgression of dog genes into coyote populations; and (c) to the probable source of the extremely large size and remarkably great variation of a population of wild, coyote-like animals recently established in New England.

It is concluded that the phase shift in the breeding season of F1 hybrids, requiring the young of animals presumably less fit than coyotes to be reared in midwinter and in the absence of male parental care should form an effective, if not absolute, block to the development of hybrid swarms and to the introgression of dog genes into the coyote gene pool. Application of discriminant functions analysis—here applied also to various hybrids—to a series of wild Kansas coyotes (which are as much exposed to dogs as any coyotes) shows that these specimens have none of the unusual variability characterizing the New England population. It is therefore concluded that the variability and large size of the New England canids result from the introgression of wolf genes, probably in Ontario, into coyote stock. Recent proof that these species can in fact hybridize is cited. Also, two captive-reared coyote-wolf hybrids, long ago reported but later widely over-looked, seem likely in fact to represent this cross if judged by discriminant functions analysis and by their small size.
43973759
DNA profiles of the eastern Canadian wolf and the red wolf provide evidence for a common evolutionary history independent of the gray wolf
The origin and taxonomy of the red wolf (Canis rufus) have been the subject of considerable debate and it has been suggested that this taxon was recently formed as a result of hybridization between the coyote and gray wolf. Like the red wolf, the eastern Canadian wolf has been characterized as a small "deer-eating" wolf that hybridizes with coyotes (Canis latrans). While studying the population of eastern Canadian wolves in Algonquin Provincial Park we recognized similarities to the red wolf, based on DNA profiles at 8 microsatellite loci. We examined whether this relationship was due to similar levels of introgressed coyote genetic material by comparing the microsatellite alleles with those of other North American populations of wolves and coyotes. These analyses indicated that it was not coyote genetic material which led to the close genetic affinity between red wolves and eastern Canadian wolves. We then examined the control region of the mitochondrial DNA (mtDNA) and confirmed the presence of coyote s...
128678108
Early Domesticated Dogs of the Near East
Domestic dogs in the Near East have been identified on the basis of cultural criteria, but identifications based on morphological criteria are controversial. Measurements of carnassial teeth and of the facial region of the cranium and mandible reveal that wolf/dog remains from the Natufian (c. 12,000 BP) and later cultures of Israel exhibit a morphological pattern that is the opposite of that expected under natural selection, but that conforms well to that expected in early domestication. The Geometric Kebaran wolves preceding the Natufian domesticates are very large individuals, probably in response to the climatic conditions of the period, and this may indicate one of the following: (a) the wolves domesticated in Israel were of a large race, contrary to previous theories on the roots of dog domestication; (b) the dog was domesticated at a period earlier than the Natufian.
86614655
Mitochondrial DNA Variability in Italian and East European Wolves: Detecting the Consequences of Small Population Size and Hybridization
The Italian wolf (Canis lupus) population has declined continuously over the last few centuries and become isolated as a result of the extermination of other populations in central Europe and the Alps dur- ing the nineteenth century. In the 1970s, approximately 100 wolves survived in 10 isolated areas in the central and southern Italian Apennines. Loss of genetic variability, as suggested by prelimzinary studies of mi- tochondrial DNA (mtDNA) sequences, hybridization with feral dogs, and the illegal release of captive, non- native wolves are considered potential threats to the viability of the Italian wolf population. We sequenced 546 base pairs of the mtDNA control region in a comnprehensive set of Italian wolves and compared thjem to those of dogs and other wolf populations from Europe and the Near East. Our data confirm the absence of mtDNA variability in Italian wolves. all 101 individuals sampled across their distribution in Italy had the same, unique haplotype, whereas seven haplotypes were found in only 26 wolves from an outbred popula- tion in Bulgaria. Most haplotypes were specific either to wolves or dogs, but some east European wolves shared haplotypes with dogs, indicative of hybridization. In contrast, neither hybridization with dogs nor in- trogression of non-native wolves was detected in the Italian population. These findings exclude the introgres- sion of dog genes via matings between male wolves and female dogs, the most likely direction of hybridiza- tion. The observed mtDNA monomorphism is the possible outcome of random drift in the declining and isolated Italian wolfpopulation, which probably existed at low effective population size during the last 100- 150 years. Low effective population size and the continued loss of genetic variability might be a major threat to the long-termn viability of Italian wolves. A controlled demographic increase, leading to recolonization of
31338101
Multiple and ancient origins of the domestic dog.
Mitochondrial DNA control region sequences were analyzed from 162 wolves at 27 localities worldwide and from 140 domestic dogs representing 67 breeds. Sequences from both dogs and wolves showed considerable diversity and supported the hypothesis that wolves were the ancestors of dogs. Most dog sequences belonged to a divergent monophyletic clade sharing no sequences with wolves. The sequence divergence within this clade suggested that dogs originated more than 100,000 years before the present. Associations of dog haplotypes with other wolf lineages indicated episodes of admixture between wolves and dogs. Repeated genetic exchange between dog and wolf populations may have been an important source of variation for artificial selection.
38549729
Hybridization and the phylogenetic relationship between polecats and domestic ferrets in Britain
Ferrets (Mustela furo) were domesticated from polecats (M. putorius, M. eversmannii) over 2000 years ago. Following their introduction to Britain, they escaped and hybridized with native European polecats (M. putorius). Native polecats declined to the point of near extinction prior to World War I, but have recently begun to expand from a Welsh refugium. Concern has arisen as to the extent of polecat/ferret introgression, and in particular, whether the expanding population is of mainly hybrid origin. Therefore, mitochondrial DNA sequencing was used to investigate polecat genetic diversity in Britain. Two geographically distinct lineages were found, where one may be ancestral to the British polecat, and the other to the domestic ferret. The ancestral distribution of each lineage, or assortative mating is sufficient to explain the observed pattern. A further comparison between the distribution of the polecat phenotype and mitochondrial haplotype implies that the current population expansion may be mediated by dispersing male polecats hybridizing with female feral ferrets. However, the wild source of the ferret remains obscure. Relatively recent speciation from European mink (M. lutreola) and black-footed ferrets (M. nigripes), and/or the effects of hybridization result in an unresolved molecular phylogeny.
41732951
Wolf-dog genetics
SummaryThe wolf and the dog can be readily crossed and the resulting hybrids are fully fertile. Typical Mendelian segregation has been demonstrated for many different characters, notably for hair colour and pattern, eye colour, ear form, size and various skull characters. There is also evidence for segregation in certain physiological peculiarities such as season of rut and nervous disposition. Modificatory influences due to environment may affect some of the craniological characters, the form of the tail and the general external appearance, though in all of these cases the differences are at basis genotypical. The bark of the dog is shown to be a purely modificatory character which may be readily acquired by the wolf. Certain features such as the duration of pregnancy, the blind period in the young, the order of appearance of milk teeth and the moulting phenomena are identical in both wolves and dogs. All of these data taken together serve to emphasize the very close similarity in genetical constitution between the wolf and the dog, and suggest thepossibility of the origin of the various races ofCanis familiaris from a single wild species, viz.C. lupus.
14164465
Analysis of coyote mitochondrial DNA genotype frequencies: estimation of the effective number of alleles.
A restriction-site survey of 327 coyotes (Canis latrans) from most parts of their North American range reveals 32 mitochondrial DNA (mtDNA) genotypes. The genotypes are not strongly partitioned in space, suggesting that there is high gene flow among coyote subpopulations. Consequently, each new geographic location added to the study has a decreasing probability of containing a mtDNA genotype that had not been previously discovered. This being the case, by using Monte Carlo sampling experiments, we can estimate the total number of genotypes that would be found if all possible localities were surveyed. This estimate of total genotypic variability agrees qualitatively with estimates based on theoretical considerations of the expected number of alleles in a stable population. We also predict effective population sizes from genotype data. The accuracy of these estimates is thought to be dependent on the fact that coyotes are not highly genetically structured, a situation which may apply to highly mobile species.
83941309
Miller's anatomy of the dog
* The Dog and Its Relatives Introduction and Breeds Phylogenetic Relationships of Canids to Other Carnivores Origin and Domestication of the Dog * Prenatal Development * The Integument * The Skeleton * Arthrology * The Muscular System * The Digestive Apparatus and Abdomen * The Respiratory System * The Urogenital System * The Endocrine System * The Heart and Arteries * The Veins * The Lymphatic System * Introduction to the Nervous System * The Autonomic Nervous System * Spinal Cord and Meninges * The Spinal Nerves * The Brain * Cranial Nerves and Cutaneous Innervation of the Head * The Ear * The Eye