Papers! Lizard patterns

Å: Intraspecific Variation in Dorsal Colour Patterns of Amphibolurus muricatus Lizards From the Perspective of Relevant Observers

Jacky dragons exhibit substantial variation in their dorsal camouflage patterns across sex, body size, genetic lineage, and habitat type, with these differences being perceived differently by conspecifics and avian predators depending on viewing distance and visual system. The findings suggest that their colour patterns have evolved under a combination of local habitat conditions and predator-driven selection pressures, reflecting the complex and observer-dependent nature of camouflage.

Abstract: The visual environment animals occupy is often comprised of spatially distinct microhabitats featuring different and varying backgrounds, lighting conditions, temperatures, feeding opportunities and threats. For species employing colouration in some capacity, efficacy can vary substantially between these; thus, we expect some variation within species to adapt to the traits of specific microhabitats. Cryptic animals can be particularly sensitive to changes or choices in habitat and predation threats and often display intraspecific variation of their colour patterns. One such species, the Jacky dragon (Amphibolurus muricatus), occurs across a wide geographic range incorporating several distinct habitat types and possesses dorsal camouflage patterns that aid in avoiding detection from a range of potential predators. Here we investigate intraspecific variation of the dorsal patterns of A. muricatus within the context of relevant observers at multiple viewing distances. Using multispectral photography, contemporary analysis software and specifically constructed visual models for the Jacky dragon and two avian predators, we quantified patterns of individuals collected across the geographic range of the species. Larger lizards appear to have more distinct dorsal patches to lizards at close range, but avian predators see reduced pattern diversity and complexity. At a distance, both predators see fewer clusters, and size has less effect. Close-­ up, males show more distinct patches, contrast and luminance to lizards, but lower contrast to kookaburras. Furthermore, differences are also apparent between genetic clades and habitat characteristics, with lizards in coastal heath exhibiting greater pattern diversity and complexity to all observers. Importantly, these differences are mediated by observer identity, as significant effects are not consistent across different visual systems. Our results suggest that variation in the visual appearance of these lizards is multifaceted and in response to both general and local selection pressures.

View the paper here: https://doi.org/10.1002/ece3.71944

B: Perch choice and substrate matching to the dorsal patterns of Amphibolurus muricatus lizards

Jacky dragons did not consistently choose the backgrounds that best matched their camouflage, but variation in background availability across locations meant that some populations occupied more closely matching habitats than others, suggesting that local environmental conditions influence both camouflage effectiveness and the evolution of dorsal pattern variation.

Abstract: The backgrounds that cryptic animals choose will affect the efficacy of their camouflage. Most animals use a range of microhabitats consisting of a variety of substrates, vegetation and lighting conditions. As some of these will be better suited to facilitating camouflage than others, we expect cryptic animals to consider their conspicuousness when choosing a background to occupy. If the availability of backgrounds varies between populations of cryptic animals, then selective pressure on their coloration may also vary, resulting in intraspecific variation and presumably animals being better suited to the backgrounds locally available to them than those at other locations. In this study we investigate how backgrounds available to Jacky dragons (Amphibolurus muricatus) vary across their range, whether these lizards are occupying backgrounds that match well to their dorsal patterns, and how backgrounds compare to their dorsal patterns. Wild lizards were located and photographed along with the background they were found on, and other options available nearby. We compared lizards and backgrounds within their microhabitat as well as all backgrounds across all microhabitats. We found that lizards were not occupying the backgrounds that best matched their own patterns, that background options varied between locations, and that lizards from certain locations were occupying backgrounds closer matching to their own pattern than those from other locations. These outcomes provide interesting insight into the variance of local factors that influence the pattern phenotype, as well as how the relative need for camouflage might vary and be balanced with other needs.

View the paper here: https://doi.org/10.1093/beheco/araf129