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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

Verification of model design for male and female model treatments. Showing the degree of model versus background contrast of a proportion (18%) of 600 clay models used in the survival experiment. Chromatic (left axis; black data points) and luminance (right axis; red data points) contrast of models against Syros and Skopelos rock backgrounds is shown, as perceived by avian predators (JND). Model treatments were designed to replicate the color and luminance of male and female Aegean wall lizards (Podarcis erhardii) from the Syros and Skopelos island populations, calibrated to a typical avian predator (peafowl; Pavo cristatus) visual system (N: males = 55; females = 53). Generally, values increasing >3.00 JND depict models that are progressively distinguishable against the background. Error bars represent mean JNDs ± 1.0 SE.
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ece31650-fig-0004: Verification of model design for male and female model treatments. Showing the degree of model versus background contrast of a proportion (18%) of 600 clay models used in the survival experiment. Chromatic (left axis; black data points) and luminance (right axis; red data points) contrast of models against Syros and Skopelos rock backgrounds is shown, as perceived by avian predators (JND). Model treatments were designed to replicate the color and luminance of male and female Aegean wall lizards (Podarcis erhardii) from the Syros and Skopelos island populations, calibrated to a typical avian predator (peafowl; Pavo cristatus) visual system (N: males = 55; females = 53). Generally, values increasing >3.00 JND depict models that are progressively distinguishable against the background. Error bars represent mean JNDs ± 1.0 SE.

Mentions: We verified that, on both islands, we achieved our planned model design to produce male models that were more conspicuous than female models (although only in terms of chromatic contrast) and this effect was more evident on Skopelos than on Syros (Fig. 4; Skopelos: F1,64 = 21.763, P < 0.001, ηp2 = 0.254; Syros: F1, 40 = 5.514, P = 0.024, ηp2 = 0.121; Skopelos males = [mean ± SE JND] 11.154 ± 0.886, Skopelos females = 6.215 ± 0.540; Syros males = 11.815 ± 0.994, Syros females = 8.466 ± 0.453).


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

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

Verification of model design for male and female model treatments. Showing the degree of model versus background contrast of a proportion (18%) of 600 clay models used in the survival experiment. Chromatic (left axis; black data points) and luminance (right axis; red data points) contrast of models against Syros and Skopelos rock backgrounds is shown, as perceived by avian predators (JND). Model treatments were designed to replicate the color and luminance of male and female Aegean wall lizards (Podarcis erhardii) from the Syros and Skopelos island populations, calibrated to a typical avian predator (peafowl; Pavo cristatus) visual system (N: males = 55; females = 53). Generally, values increasing >3.00 JND depict models that are progressively distinguishable against the background. Error bars represent mean JNDs ± 1.0 SE.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4588654&req=5

ece31650-fig-0004: Verification of model design for male and female model treatments. Showing the degree of model versus background contrast of a proportion (18%) of 600 clay models used in the survival experiment. Chromatic (left axis; black data points) and luminance (right axis; red data points) contrast of models against Syros and Skopelos rock backgrounds is shown, as perceived by avian predators (JND). Model treatments were designed to replicate the color and luminance of male and female Aegean wall lizards (Podarcis erhardii) from the Syros and Skopelos island populations, calibrated to a typical avian predator (peafowl; Pavo cristatus) visual system (N: males = 55; females = 53). Generally, values increasing >3.00 JND depict models that are progressively distinguishable against the background. Error bars represent mean JNDs ± 1.0 SE.
Mentions: We verified that, on both islands, we achieved our planned model design to produce male models that were more conspicuous than female models (although only in terms of chromatic contrast) and this effect was more evident on Skopelos than on Syros (Fig. 4; Skopelos: F1,64 = 21.763, P < 0.001, ηp2 = 0.254; Syros: F1, 40 = 5.514, P = 0.024, ηp2 = 0.121; Skopelos males = [mean ± SE JND] 11.154 ± 0.886, Skopelos females = 6.215 ± 0.540; Syros males = 11.815 ± 0.994, Syros females = 8.466 ± 0.453).

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