Conspicuous male coloration impairs survival against avian predators in Aegean wall lizards, Podarcis erhardii

Abstract

Animal coloration is strikingly diverse in nature. Within‐species color variation can arise through local adaptation for camouflage, sexual dimorphism and conspicuous sexual signals, which often have conflicting effects on survival. Here, we tested whether color variation between two island populations of Aegean wall lizards (Podarcis erhardii) is due to sexual dimorphism and differential survival of individuals varying in appearance. On both islands, we measured attack rates by wild avian predators on clay models matching the coloration of real male and female P. erhardii from each island population, modeled to avian predator vision. Avian predator attack rates differed among model treatments, although only on one island. Male‐colored models, which were more conspicuous against their experimental backgrounds to avian predators, were accordingly detected and attacked more frequently by birds than less conspicuous female‐colored models. This suggests that female coloration has evolved primarily under selection for camouflage, whereas sexually competing males exhibit costly conspicuous coloration. Unexpectedly, there was no difference in avian attack frequency between local and non‐local model types. This may have arisen if the models did not resemble lizard coloration with sufficient precision, or if real lizards behaviorally choose backgrounds that improve camouflage. Overall, these results show that sexually dimorphic coloration can affect the risk of predator attacks, indicating that color variation within a species can be caused by interactions between natural and sexual selection. However, more work is needed to determine how these findings depend on the island environment that each population inhabits.

A different kind of ecological modelling: the use of clay model organisms to explore predator–prey interactions in vertebrates

“…Sometimes accuracy of appearance is vital, when the models are intended to look, to predators, like a particular species or local variant of a species. Marshall, Philpot & Stevens () used reflectance spectrometry measurements of Aegean wall lizards Podarcis erhardii to alter the colour of the clay used to make lizard models in an effort to mimic the colour as part of their test for the contribution of sexual dimorphism and local variation to predation rates by birds. Similarly, Stuart‐Fox et al .…”

Risk of social colours in an agamid lizard: implications for the evolution of dynamic signals

“…Furthermore, higher predator attacks on male models compared to females were not due to their larger size. One of the central predictions of sexual selection is that males, and not females, are expected to express conspicuous colours [3] as males have greater selection pressure to signal to competitors and mates [26,27]. As demonstrated here, conspicuous colours can have a significant predation cost.…”

Broad‐scale variation in sexual dichromatism in songbirds is not explained by sex differences in exposure to predators during incubation

“…Sexual selection is therefore insufficient to explain all the variation in sexual dichromatism. Second, in natural populations of lizards predators were shown to prefer more colorful males (Stuart-Fox et al 2003, Marshall et al 2015, and in detailed studies of fish, males were subsequently less brightly colored in populations suffering higher risk of predation (Endler 1980, 1983, 1991, Ruell et al 2013. His view has recently been supported by two observations.…”

“…First, detailed phylogenetic studies of several avian clades suggested that dichromatism arose due to females becoming less conspicuous rather than males becoming brighter (Friedman et al 2009, Dale et al 2015. Second, in natural populations of lizards predators were shown to prefer more colorful males (Stuart-Fox et al 2003, Marshall et al 2015, and in detailed studies of fish, males were subsequently less brightly colored in populations suffering higher risk of predation (Endler 1980, 1983, 1991, Ruell et al 2013. Generally, if the strength, or even direction, of selection pressure on coloration is different for males and females, the evolutionary outcome should be sexual dichromatism (Cox and Calsbeek 2009).…”