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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

Above: The five model treatments used in the survival experiments (left to right): brown control (unmatched to real lizard coloration), Syros male, Syros female, Skopelos male, and Skopelos female. Below: examples of avian and non‐avian attacks on models.
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ece31650-fig-0003: Above: The five model treatments used in the survival experiments (left to right): brown control (unmatched to real lizard coloration), Syros male, Syros female, Skopelos male, and Skopelos female. Below: examples of avian and non‐avian attacks on models.

Mentions: We checked all models at 24‐, 48‐, 72‐, 96‐, and 120‐h intervals and noted any signs of predator attacks. Models with attack marks on them were noted as attacked, removed, and not replaced to minimize how many models were encountered by the same predator, as is typical in this type of experiment (e.g., Cuthill et al. 2005; Stevens et al. 2006; Stobbe and Schaefer 2008; Farallo and Forstner 2012). We classified models that exhibited unambiguous clear triangular beak/stab marks together with obvious signs of attack (flipped over, in pieces and/or moved) as attacked by avian predators (see Fig. 3). For instance, some models were found with beak/stab marks on the head, often so that the head was separated from the body, and one model's head was found 10 m away in a nearby field. Occasionally, we found models that had been pecked all over were in pieces and/or overturned and far away from the original location. When checking the models, we noted where on the model avian attack marks were found. These were classified into three locations of attack: (1) only head, (2) only body (including body, legs, and tail), and (3) both head and body. Models that had heads missing or that were separated from the body were classified as attacked on the head if no other body part showed attack marks. Models with small teeth marks or any other marks were classified as attacked by non‐avian predators (e.g., snakes, rodents, and insects) (see Fig. 3). We recorded models with no marks after 120‐h as not attacked. We classified any models that could not be found as missing, although the possibility that a bird had seized and flown off with them was considered in the analysis. Specifically, we performed two survival analyses: (1) with the missing models treated as unattacked (censored) and (2) with missing models classified as attacked. We qualitatively compared the results of the two analyses to determine any differences due to missing models being classified as attacked or unattacked.


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

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

Above: The five model treatments used in the survival experiments (left to right): brown control (unmatched to real lizard coloration), Syros male, Syros female, Skopelos male, and Skopelos female. Below: examples of avian and non‐avian attacks on models.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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ece31650-fig-0003: Above: The five model treatments used in the survival experiments (left to right): brown control (unmatched to real lizard coloration), Syros male, Syros female, Skopelos male, and Skopelos female. Below: examples of avian and non‐avian attacks on models.
Mentions: We checked all models at 24‐, 48‐, 72‐, 96‐, and 120‐h intervals and noted any signs of predator attacks. Models with attack marks on them were noted as attacked, removed, and not replaced to minimize how many models were encountered by the same predator, as is typical in this type of experiment (e.g., Cuthill et al. 2005; Stevens et al. 2006; Stobbe and Schaefer 2008; Farallo and Forstner 2012). We classified models that exhibited unambiguous clear triangular beak/stab marks together with obvious signs of attack (flipped over, in pieces and/or moved) as attacked by avian predators (see Fig. 3). For instance, some models were found with beak/stab marks on the head, often so that the head was separated from the body, and one model's head was found 10 m away in a nearby field. Occasionally, we found models that had been pecked all over were in pieces and/or overturned and far away from the original location. When checking the models, we noted where on the model avian attack marks were found. These were classified into three locations of attack: (1) only head, (2) only body (including body, legs, and tail), and (3) both head and body. Models that had heads missing or that were separated from the body were classified as attacked on the head if no other body part showed attack marks. Models with small teeth marks or any other marks were classified as attacked by non‐avian predators (e.g., snakes, rodents, and insects) (see Fig. 3). We recorded models with no marks after 120‐h as not attacked. We classified any models that could not be found as missing, although the possibility that a bird had seized and flown off with them was considered in the analysis. Specifically, we performed two survival analyses: (1) with the missing models treated as unattacked (censored) and (2) with missing models classified as attacked. We qualitatively compared the results of the two analyses to determine any differences due to missing models being classified as attacked or unattacked.

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