US EPA

4315034 

Journal Article 

The lizard Psammodromus algirus (Squamata: Lacertidae) is darker at high altitudes 

Reguera, S; Zamora-Camacho, FJ; Moreno-Rueda, G 

2014 

Yes 

Biological Journal of the Linnean Society
ISSN: 0024-4066
EISSN: 1095-8312 

112 

1 

132-141 

10.1111/bij.12250 

WOS:000334463800011 

Altitudinal gradients offer a good opportunity to study organisms' adaptations to clinal environmental variables. Regarding altitude, the most influential variables on organisms are temperature and ultraviolet (UV) solar radiation, the first decreasing and the second increasing with altitude. Both variables affect ectotherms' biology, as ectotherms depend on environmental temperature for thermoregulation, frequently being heliotherms. Here, we studied dorsal coloration in the lizard Psammodromus algirus (Linnaeus, 1758) along a wide altitudinal gradient (2200 m) in Sierra Nevada (south-east Spain). We hypothesize that the skin will be darker with altitude, i.e. in environments with lower temperatures and higher UV radiation intensity. Results show that individual dorsal colorations became darker at high altitude. We propose two non-mutually exclusive explanations for this result: (1) darker dorsal surface would favour faster warming at high altitudes, where temperature is lower, and (2) darker dorsal surface would protect against UV radiation, stronger at high altitudes. We found significant relationships between both temperature and UV radiation and population dorsal darkness, giving mixed support for the two explanations. Moreover, dorsal hue was positively correlated with substrate hue, suggesting that hue evolved to maximize crypsis. Our study therefore suggests that geographical variation in dorsal coloration in this lizard is adaptive, and darkness coloration might have evolved in response to adverse conditions (low temperature and high UV radiation) at high altitudes. (c) 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014,112, 132-141. 

body colour; altitudinal gradient; ultraviolet radiation; thermal melanism; darkened coloration