Environmental correlates of morphological diversity in Australian geckos.

Aim: Climatic variation has long been regarded as a primary source of morphological variation. However, there is mixed support for the adherence of reptiles to ecogeographical hypotheses, such as Bergmann's rule (body size decreases with temperature) and Allen's rule (limb length increases with temperature). We quantified body and limb morphology among the diverse Australian gecko fauna (4 families, 30 genera, 226 of the 231 described species) to investigate environmental correlates of morphological variation in this radiation. Location: Australia. Major taxa studied: Geckos (Squamata: Gekkota; the families Gekkonidae, Carphodactylidae, Diplodactylidae and Pygopodidae). Methods: We measured 20 external features of ethanol‐preserved museum specimens. We investigated whether principal component axes of morphology were correlated with three key environmental variables, and the microhabitat occupied by each species. Results: Morphology varied greatly among Australian gecko families and genera, although there was a strong phylogenetic signal in morphology. After accounting for phylogeny, morphology was correlated with a species' microhabitat use. Saxicolous species and species with variable microhabitat requirements (i.e., generalists) had larger body dimensions than terrestrial species. Saxicolous species also had longer proportional forelimbs and hindlimbs than terrestrial species. Main conclusions: Our results highlight the importance of phylogeny and microhabitat use in shaping the morphology of Australian geckos. We find little evidence that Australian geckos adhere to Bergmann's rule or Allen's rule, suggesting that these ecogeographical hypotheses provide limited insight into the adaptive potential of lizard species to altered environmental conditions. [ABSTRACT FROM AUTHOR]