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

Marshall KL, Philpot KE, Stevens M - Ecol Evol (2015)

Bottom Line: Within-species color variation can arise through local adaptation for camouflage, sexual dimorphism and conspicuous sexual signals, which often have conflicting effects on survival.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology University of Cambridge Cambridge CB2 3EJ UK.

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.

No MeSH data available.


Related in: MedlinePlus

Example images of Aegean wall lizards (Podarcis erhardii) and equivalent model replicas. Male and female P. erhardii from the focal Skopelos and Syros populations are shown alongside the models that were designed to resemble their size, shape, color, and brightness (luminance). Note that the models are calibrated to violet‐sensitive (VS) avian predator color vision, whereas images of lizards are perceived by the human visual system.
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ece31650-fig-0001: Example images of Aegean wall lizards (Podarcis erhardii) and equivalent model replicas. Male and female P. erhardii from the focal Skopelos and Syros populations are shown alongside the models that were designed to resemble their size, shape, color, and brightness (luminance). Note that the models are calibrated to violet‐sensitive (VS) avian predator color vision, whereas images of lizards are perceived by the human visual system.

Mentions: Models were designed to resemble the dorsal color and luminance of Syros and Skopelos male and female P. erhardii as modeled to avian vision. Specifically, because anterior and posterior dorsal coloration of P. erhardii can vary (Fig. 1; Marshall and Stevens 2014), we designed the models so that the clay colors matched, as closely as possible, an average avian photon catch of the anterior and posterior dorsal regions in both male and female lizards from each island population (derived from image analysis and visual modeling, as described above). Although imperfect, we used the average dorsal coloration as our lizard color reference for two reasons. First, because P. erhardii dorsal coloration can be extremely variable, even within the same sex (see Fig. 1), so that achieving accurate replicas of all types of dorsal coloration would be very difficult. Second, we aimed to design models so that they resembled the coloration of all dorsal regions potentially viewed by aerial predators. An average coloration of the anterior and posterior regions facilitated this given the difficulty of finding clay colors that closely matched avian‐perceived lizard coloration (see below). We acknowledge, however, that at relatively close range, different parts of lizards' backs may not have the same detection probabilities.


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

Marshall KL, Philpot KE, Stevens M - Ecol Evol (2015)

Example images of Aegean wall lizards (Podarcis erhardii) and equivalent model replicas. Male and female P. erhardii from the focal Skopelos and Syros populations are shown alongside the models that were designed to resemble their size, shape, color, and brightness (luminance). Note that the models are calibrated to violet‐sensitive (VS) avian predator color vision, whereas images of lizards are perceived by the human visual system.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4588654&req=5

ece31650-fig-0001: Example images of Aegean wall lizards (Podarcis erhardii) and equivalent model replicas. Male and female P. erhardii from the focal Skopelos and Syros populations are shown alongside the models that were designed to resemble their size, shape, color, and brightness (luminance). Note that the models are calibrated to violet‐sensitive (VS) avian predator color vision, whereas images of lizards are perceived by the human visual system.
Mentions: Models were designed to resemble the dorsal color and luminance of Syros and Skopelos male and female P. erhardii as modeled to avian vision. Specifically, because anterior and posterior dorsal coloration of P. erhardii can vary (Fig. 1; Marshall and Stevens 2014), we designed the models so that the clay colors matched, as closely as possible, an average avian photon catch of the anterior and posterior dorsal regions in both male and female lizards from each island population (derived from image analysis and visual modeling, as described above). Although imperfect, we used the average dorsal coloration as our lizard color reference for two reasons. First, because P. erhardii dorsal coloration can be extremely variable, even within the same sex (see Fig. 1), so that achieving accurate replicas of all types of dorsal coloration would be very difficult. Second, we aimed to design models so that they resembled the coloration of all dorsal regions potentially viewed by aerial predators. An average coloration of the anterior and posterior regions facilitated this given the difficulty of finding clay colors that closely matched avian‐perceived lizard coloration (see below). We acknowledge, however, that at relatively close range, different parts of lizards' backs may not have the same detection probabilities.

Bottom Line: Within-species color variation can arise through local adaptation for camouflage, sexual dimorphism and conspicuous sexual signals, which often have conflicting effects on survival.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology University of Cambridge Cambridge CB2 3EJ UK.

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.

No MeSH data available.


Related in: MedlinePlus