Relations between microhabitat use and limb shape in phrynosomatid lizards

Abstract

With the exception of the well-documented case for anoline lizards, recent studies have found few evolutionary relationships between morphology and habitat use in lizards despite clear-cut biomechanical predictions. One of the factors typically hampering these analyses is the clustering of habitat use within evolutionary lineages. In the present study, body shape was quantified for male and female lizards of 30 species of phrynosomatid lizards. This group was selected as little clustering of ecological variables seemed to be present. The results of traditional analyses indicate that evolutionary correlates of habitat use were prominent in the hindlimbs of both sexes. Species living in open habitats are characterized by longer femurs, and longer hindlimbs relative to the forelimb. Moreover, males from ground-dwelling species utilizing open habitats have longer toes on the hind foot than males from climbing species. Phylogenetic analyses indicated strong evolutionary associations between habitat use and the relative length of front and hindlimbs, with species from open terrestrial habitats having significantly shorter frontlimbs relative to their hindlimb than rock or tree climbing species. Evolutionary associations between morphology and habitat use were generally stronger for male lizards, indicating a potentially important contribution of sexual selection to the evolution of differences in limb proportions.