It ain’t easy being orange: lizard colour morphs occupying highly vegetated microhabitats suffer greater ectoparasitism

Abstract

Intraspecific colour morphs usually differ in more traits than just colour. These traits can manifest as differences in morph physiology, behaviour, and ecology. Ecological differences among colour morphs, such as the degree of parasitism, can influence the evolution, maintenance, and loss of morphs from populations. High ectoparasite load can directly and deleteriously impact host fitness, and thus could influence colour morph persistence in populations if certain morphs are more frequently exposed to parasites or are more susceptible to parasitism. The Aegean wall lizard, Podarcis erhardii, is a colour polymorphic island lizard that is parasitized externally by ticks and mites. These ectoparasites can affect aspects of host lizard behaviour and physiology – including thermoregulation and body mass – and therefore are an important factor influencing the ecology and fitness of P. erhardii. We find that among sympatric colour morphs, ectoparasite loads differ; namely, monochromatic orange morphs have the highest numbers of ectoparasites, and in general, morphs with orange alleles (orange, orange-white, and orange-yellow) are more heavily parasitized by ticks and mites than the other morphs. Our results indicate that morphs with orange alleles tend to occupy microhabitats with significantly more vegetation cover and thus may increase their exposure to ticks and mites. Ecological differences between morphs could be an important factor contributing to demonstrated patterns of orange morph rarity and loss in P. erhardii populations.

Some like it hotter: differential thermal preferences among lizard color morphs

“…We found significant support for our hypothesis that the brighter, larger orange morphs would prefer cooler temperatures compared to the white and yellow morphs (Figure 3), which we had based on their observed preference for microhabitats that offer cooler, shadier conditions (BeVier et al, 2022). A hypothesized consequence of color polymorphism is the evolution of morphs that have non-overlapping environmental resource use and distinct thermal physiologies (West-Eberhard, 1986; Galeotti & Rubolini, 2004; Forsman & Åberg, 2008; Forsman et al, 2008).…”

“…Overall, our results provide more evidence that P. erhardii color morphs have alternative trait combinations and for that reason may utilize different environmental resources (BeVier et al, 2022;Brock & Madden, 2022;Brock et al, 2022a). Morph differences in temperature preference have profound implications for morph coexistence and morph life histories, especially in thermally sensitive species like ectotherms.…”

“…Like many Podarcis lizards, adult P. erhardii have three genetically determined throat color morphs that are orange, white, or yellow (Andrade et al, 2019; Brock et al, 2022c; Figure 1). Podarcis erhardii color morphs differ in throat color brightness (Brock et al, 2020), body size, behavior (Brock et al, 2022a), and habitat use (BeVier et al, 2022; Brock & Madden, 2022), which are traits that could have implications for morph differences in thermal preferences (Digby, 1955; Forsman, 2000). In general, P. erhardii orange morphs and white morphs tend to be most different from each other in these traits, and yellow morphs usually exhibit intermediate phenotypes in a suite of physical and behavioral traits (Brock et al, 2020).…”

“…Orange males are larger than white and yellow males, and female color morphs do not differ significantly in size (Brock et al, 2020), though orange females tend to be on the larger end of the size spectrum. Orange morphs are found more often in microhabitats that have more vegetation and are cooler; in contrast, white and yellow morphs are more often found in areas that are open and hotter (BeVier et al, 2022). In laboratory behavioral experiments conducted on male color morphs, orange morphs were the least bold and aggressive, yellow morphs were intermediate, and white morphs were the most active, aggressive, and adept at winning contests over limited open basking space (Brock et al, 2022a).…”

“…We hypothesize that orange color morphs prefer cooler temperatures than white and yellow morphs due to their more frequent use of darker, cooler microhabitat. Given their similar choices for microhabitat that is open and hotter (Brock & Madden, 2022; BeVier et al, 2022), we hypothesize that white and yellow morphs would not have significantly different preferred temperatures from one another. Past experimental and natural observations of P. erhardii behavior indicate that white morphs are more active than other morphs (Brock & Madden, 2022; Brock et al, 2022a); because of this, we also hypothesized that white morphs should shuttle more between cooler and hotter temperatures.…”