Abstract
Predation usually selects for visual crypsis, the colour matching between an animal and its background. Geographic co-variation between animal and background colourations is well known, but how crypsis varies along elevational gradients remains unknown. We predict that dorsal colouration in the lizard Psammodromus algirus should covary with the colour of bare soil—where this lizard is mainly found—along a 2200 m elevational gradient in Sierra Nevada (SE Spain). Moreover, we predict that crypsis should decrease with elevation for two reasons: (1) Predation pressure typically decreases with elevation, and (2) at high elevation, dorsal colouration is under conflicting selection for both crypsis and thermoregulation. By means of standardised photographies of the substratum and colourimetric measurements of lizard dorsal skin, we tested the colour matching between lizard dorsum and background. We found that, along the gradient, lizard dorsal colouration covaried with the colouration of bare soil, but not with other background elements where the lizard is rarely detected. Moreover, supporting our prediction, the degree of crypsis against bare soil decreased with elevation. Hence, our findings suggest local adaptation for crypsis in this lizard along an elevational gradient, but this local adaptation would be hindered at high elevations.
Highlights
Predation is the major cause of animal mortality in the wild [1], thereby being one of the main selective pressures in nature
In a previous study on dorsal colouration of the lizard Psammodromus algirus [45], we reported that hue, a component of colouration, was correlated with substrate hue along an elevational gradient, suggesting that dorsal colouration varied along the ecological gradient in order to favour crypsis at a local scale
We tested three predictions relative to the evolution of crypsis in the lizard P. algirus along an elevational gradient: (1) Dorsal colour will be more similar to bare soil colour than to rock substrate or grass colour; (2) dorsal colour will covary with bare soil colour along the elevational gradient; and (3) the accuracy of crypsis should decrease with elevation
Summary
Predation is the major cause of animal mortality in the wild [1], thereby being one of the main selective pressures in nature. In a previous study on dorsal colouration of the lizard Psammodromus algirus [45], we reported that hue, a component of colouration, was correlated with substrate hue along an elevational gradient, suggesting that dorsal colouration varied along the ecological gradient in order to favour crypsis at a local scale. We predict (iii) that the degree of crypsis should decrease with elevation, as a consequence of reduced predation pressure (see above), and because the lizard P. algirus shows darker colouration with increased elevation, presumably to improve thermoregulation and/or protection against UV radiation [45], which may conflict with crypsis at high elevations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
