Climate-Correlated Phenotypes in Caucasian Rock Lizards (Squamata: Lacertidae)

Lacertid head phenotypes can be driven by a combined effect of multiple selective pressures. Diet, in particular, has a strong influence on head shape; individuals with robust heads typically possess stronger bite forces, allowing them to consume harder or a broader range of prey. Given that climate directly affects the hardness and abundance of insects, we used climatic variables as a proxy for habitat-specific prey availability and tested whether head shapes of rock-dwelling and ground-dwelling Darevskia species were correlated with climatic variables present at their sampling sites. The results varied across species and sexes. In some groups, these correlations aligned with phenotypic changes commonly associated with the trophic adaptations typical of certain climatic conditions observed in most lizards. Climate-related variation in head width was more constrained in males than in conspecific females, possibly due to sexual selection favoring stronger biting forces. Similarly, variation in head width and depth was more restricted in rock-dwelling species than in ground-dwelling species, possibly reflecting the specialized heads of rock-dwellers, adapted for rocky terrains. Overall, our approach provides a simple way to evaluate the general differences in environmentally induced phenotypic plasticity between rock- and ground-dwelling species.