Walking or hanging: the role of habitat use for body shape evolution in lacertid lizards

Differences in habitat use impose ecological constraints which in turn
lead to functional and morphological differences through adaptation. In
fact, a convergent evolutionary pattern is evident when species exhibit
similar responses to similar environments. In this study we examine how
habitat use influences the evolution of body shape in lizards from the
family Lacertidae. We divided our species set into two categories:
ground-dwellers and climbers, which encompasses the verticality and
horizontality aspects of the habitat. We performed phylogenetic
comparative analyses employing 186 species and seven linear morphological
traits. Our results show contrasting patterns between head and limb shape,
which are considered distinct functional blocks. We observed differences
in forelimb proportions, but not in hindlimb length, contrary to what was
documented in other lizard groups, demonstrating a novel axis in the
limb-locomotion-habitat relationship in this family. In addition, a clear
effect of habitat use on head shape was detected. We observed that
climbing species present on average flatter heads than ground-dwelling
species, as well as different evolutionary trajectories. These findings
suggest the complex interplay between habitat use and morphological
evolution in lizards, highlighting how distinct selective pressures drive
divergent adaptations in different functional traits.