Abstract
ABSTRACTEnvironmental heterogeneity on a spatial and temporal scale fosters an organism's capacity to plastically alter coloration. Predation risk might favour the evolution of phenotypic plasticity in colour patterns, as individuals who change colour throughout the year may be able to improve their fitness. Here we explored the change in dorsal pigmentation of the Italian wall lizard (Podarcis siculus campestris) at three time points (March, July, October) during a period of activity in a Mediterranean natural area in southern Italy. Following a preliminary investigation conducted in 2018, during 2019 we captured 135 lizards and took a picture of their ventral scales to check for possible recapture over the sessions. Lizard dorsal pictures were collected in the field with the support of a reference chart to quantitatively estimate chromatic variables (hue, saturation and value). At the same time, pictures of the environmental background were collected. Our findings suggest that lizards are capable of altering dorsal coloration during seasonal change. They vary from green at the onset of spring, to brownish in the middle of summer and to a greyish colour in October. This modification closely followed environmental background colour variation and enhanced lizard crypsis during each season.
Highlights
Differences in cryptic coloration among animals have provided evidence for significant selective advantages in specific contexts [1,2,3]
We explored the possible differences between sexes in colour variation, and whether it might enhance concealment by tracking environmental modifications which occur during seasonal changes
Our findings reveal that at the start of spring, animals show a typical green colouration with greater hue values with respect to both those saturation and lightness; during summer, lizards exhibit a less lively dorsal colour tending to brownish, with a strong decrease of the average hue; at the beginning of autumn, dorsal colouration shifts to greyish with an increase in hue and a reduction in saturation, which corresponds to a grouping of both green and brownish lizards
Summary
Differences in cryptic coloration among animals have provided evidence for significant selective advantages in specific contexts [1,2,3]. Natural populations provide examples of habitat-specific body colours in a great diversity of taxa, including freshwater fish [7], frogs [8], salamanders [9], turtles [10], lizards [11], and mice [2] Such studies suggest that the adjustment to habitat-specific variation in colour is mostly a result of selective pressure by predators hunting by sight, leading the population towards an adaptive match to the local background. The tropical butterfly Bicyclus anynana shows seasonal variation in wing patterns, following the temperature which anticipates seasonal change in vegetation [13]; the snowshoe hare (Lepus americanus) goes through seasonal coat colour shifts from brown to white This change has been recorded to be strongly related to survival [14]. We explored the possible differences between sexes in colour variation, and whether it might enhance concealment by tracking environmental modifications which occur during seasonal changes
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