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- sexual selection (2) (entfernen)
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Background
In many species males face a higher predation risk than females because males display elaborate traits that evolved under sexual selection, which may attract not only females but also predators. Females are, therefore, predicted to avoid such conspicuous males under predation risk. The present study was designed to investigate predator-induced changes of female mating preferences in Atlantic mollies (Poecilia mexicana). Males of this species show a pronounced polymorphism in body size and coloration, and females prefer large, colorful males in the absence of predators.
Results
In dichotomous choice tests predator-naïve (lab-reared) females altered their initial preference for larger males in the presence of the cichlid Cichlasoma salvini, a natural predator of P. mexicana, and preferred small males instead. This effect was considerably weaker when females were confronted visually with the non-piscivorous cichlid Vieja bifasciata or the introduced non-piscivorous Nile tilapia (Oreochromis niloticus). In contrast, predator experienced (wild-caught) females did not respond to the same extent to the presence of a predator, most likely due to a learned ability to evaluate their predators' motivation to prey.
Conclusions
Our study highlights that (a) predatory fish can have a profound influence on the expression of mating preferences of their prey (thus potentially affecting the strength of sexual selection), and females may alter their mate choice behavior strategically to reduce their own exposure to predators. (b) Prey species can evolve visual predator recognition mechanisms and alter their mate choice only when a natural predator is present. (c) Finally, experiential effects can play an important role, and prey species may learn to evaluate the motivational state of their predators.
Amphibians have developed a large set of life-history strategies and demonstrate an impressive diversity of reproductive patterns compared to other vertebrates. Various selection pressures impact on males and females and see them produce different degrees of sexual dimorphism in order to maximise their reproductive success. In an extended morphometric analysis that included 27 body-and head-related characters, we studied the pattern of sexual dimorphism of a French population of the marbled newt, Triturus marmoratus. We analysed the characters by employing GLM methods (ANCOVA) and found 16 of them to be dimorphic between the sexes. In general, females differ in head-body size, such as snout-vent length, but males rather in shape or body proportions (e.g., limb proportions). The various expressions of sexual size dimorphism among large-bodied marbled newts and allies demonstrate that more than one evolutionary model works simultaneously on different traits.