Comparative Morphometrics in Leptodactyline Frogs (Anura, Leptodactylidae, Leptodactylinae): Does Burrowing Behavior Relate to Sexual Dimorphism?

Abstract

Fossorial habits occur in many animal lineages and usually involve both morphological and physiological adaptations that may evolve independently. Burrowing behavior in some species of the anuran subfamily Leptodactylinae involves the specialized use of the hind limbs and/or head. The aim of this study was to identify the morphometric characters associated with burrowing behavior in species of this subfamily. We then hypothesized that, as this habit is usually associated with males, we would find sexual dimorphism in head and hind-limb morphology in the burrowing species but not in the nonburrowing species. We compared 500 specimens from 24 species using phylogenetic statistical analyses and phylogenetic mapping of sexually dimorphic characters. The results demonstrated the following: 1) There was no correlation between the measurements of the limbs, head, or tarsal tubercle and burrowing behavior in the analyzed species; 2) there was no sexual dimorphism related to burrowing behavior reflected in measurements of the head or hind limbs; and 3) sexual dimorphism in the morphometric characters always was derived. Modifications of the ridged snout and increased ossification in the nasal region of the males of the fossorial species appear to be sufficient adaptations for burrowing.