Phenotypic variability in larvae of two species of Mediterranean spadefoot toad: an approach using linear and geometric morphometrics

Abstract

Two species of the genus Pelobates occur in the western Mediterranean region: Pelobates cultripes, in the Iberian Peninsula and southern France, and Pelobates varaldii, endemic in northwestern Morocco. These two species form a monophyletic clade within the Eurasian Pelobates and are morphologically conservative. However some morphological differences exist in their larval stages, which have been used to support the distinction between them as separate species. Here we examine the larval morphology at the premetamorphic Gosner stages of both species using linear and geometric morphometrics. The aims were: (i) to investigate the morphological variability of P. varaldii and P. cultripes and (ii) to revise the validity of the taxonomic criteria used to differentiate the larvae of these species. Our analysis revealed high intraspecific variability in both species, especially in the dorso-ventral axis, but without a geographical structure. Our results suggested the existence of morphological divergence between the larvae of P. varaldii and those of P. cultripes: P. cultripes showed a more depressed shape than P. varaldii.