The occurrence of multiple phenotypes within a sex of a single species has long puzzled behavioral ecologists. Male red-backed fairy-wrens Malurus melanocephalus exhibit 3 behaviorally distinct types in their first breeding season: breed in bright nuptial plumage, breed in dull plumage, or remain as an unpaired auxiliary (helper) with dull plumage. The retention of dull plumage by auxiliaries and dull breeders is an example of delayed plumage maturation (DPM), a widespread phenomenon in birds whose costs and benefits are not well understood. At a mechanistic level, DPM might allow dull males either to deceptively mimic females (female mimicry hypothesis) or to honestly signal their subordinate status (status-signaling hypothesis). DPM might function via either mechanism to provide ultimate benefits relative to developing nuptial plumage by increasing reproductive success, survival, or both. In this study, we tested the hypothesis that DPM is related to increased male survival in the red-backed fairy-wren via either female mimicry or status signaling. Aviary-based experiments revealed that dull males were perceived as male, which is consistent with the status-signaling hypothesis but contradicts the female mimicry hypothesis. Further aviary and field-based experiments also revealed that dull males were socially subordinate to bright males and received less aggression than bright males, further evidence for status signaling. However, male survival was not related to plumage coloration or breeding status. These findings indicate that male plumage coloration signals social status but that dull plumage does not afford a net survival advantage, perhaps because plumage color is a conditional strategy.
Feminine Mimicry and Masquerade I - Columbia University
Some of the most spectacular and best studied cases of Batesian polymorphism are found in swallowtails, and in some species only the female is mimetic (see an example in Fig. 5). This peculiar tendency to sex-specific polymorphism seems to be restricted to butterflies (Papilionidae and Pieridae), and virtually no other case of sex-limited mimicry seems to be reported for other insects (except for male-limited mimicry in some moths). Female-limited mimicry was often viewed as a result of negative frequency dependence: if mimicry is restricted to one sex, the effective mimetic population size is only about half that of a nondimorphic species, reducing deleterious effects of parasitism onto the warning signal. But this group-selection argument cannot in itself explain why females tend to become mimetic more often than males and why mechanisms arise that restrict the mimicry to one sex. However, more proximal, individual-selection arguments are not lacking. First, mimicry may be more beneficial to one sex than to the other. For instance, female butterflies have a less agile flight because of egg load and a more “predictable” flight when searching oviposition sites, and they suffer higher rates of attacks by visual predators. Second, male wing patterns can
FIGURE 5 Female-limited mimicry in Perrhybris pyrrha (Pieridae), Eastern Peru. The female (top) is a Batesian mimic of the tiger-patterned Ithomiines and Helicomiines (see Fig. 3- , while the male (bottom) has retained a typical pierid white coloration. Scale bar, 2 cm.
be constrained by sexual selection, via either female choice or male-male interactions: males could not evolve Batesian mimicry without losing mating opportunities. In experiments with North American swallowtails (of which only females mimic B. philenor), male P. glaucus painted with the mimetic pattern had a lower mating success than normal yellow males; similarly, painted P. polyxenes males had a lower success in male-male fights and therefore held lower-quality territories around hilltops. In these insects, the wing coloration appears to bear signals directed either to conspecific males or to predators, which creates a potential conflict leading to sex-limited polymorphism. It is interesting to note that Papilio and Eurytides species that mimic Parides (Papilionidae) in South America do not exhibit female-limited mimicry; different modes of sexual selection (e.g., absence of territoriality) may operate in the forest understory habitat. In a different ecological setting, diurnal males of the North American silkmoth C. promethea are exposed to visual predators, and mimicry of B. philenor is limited to males; female Callosamia fly at night and benefit more by crypsis during the day.
FEMININE MIMICRY AND MASQUERADE 91 ..
Bluegill males are characterized by a discrete life history polymorphism. "Parental" males mature at age 7, and have several reproductive years before they die. These males use their caudal fins to construct bowl-shaped nests in colonies that may be as small as 10 nests, but may have more than 100. Parental males then court females and defend and care for the young for the length of the care-giving period (7-10 days). These males are approximately 20cm long and have a mass of close to 200g. "Cuckolder" males, in contrast, mature at age 2. They do not provide care for the young, and instead fertilize eggs opportunistically using one of two different tactics. "Sneaker" males are small (7-10cm total length) individuals 2-3 years old. When a female has entered a nest to spawn with the nest-guarding parental male, sneakers swim very quickly into the nest, usually beneath the spawning pair, and release their sperm. "Satellite" males (also called "Female mimics") are larger (10-14cm total length) and older (4-6 years). Rather than sneak into the nest, satellites mimic the appearance and behaviour of females. They enter the nest as a parental male and a female are in the act of spawning, but release sperm rather than eggs, thus stealing fertilizations from the parental male. In approximately 90% of cases, parental males are alone with females in the nest. However, in the cases in which males are in competition for fertilizations, cuckolders fertilize the majority of eggs released. On average, approximately one-fifth of larvae in a parental's nest were sired by cuckolder males. Females provide no care to the developing larvae. They mature at age 4 and enter colonies as a shoal to spawn. A parental male will have multiple females visit his nest, and females will visit the nest of multiple males. In Lake Opinicon, bluegill breed in June, with some spawning bouts occuring in late May and early July. Most adults participate in multiple spawning bouts in a year.
Female mimicry in garter snakes (PDF Download Available)