Morphological variation inBlommersiapelvic shape coincides with muscular architecture and parallels genus phylogenetic evolution

Abstract

Mantellids are a hyperdiverse group of frogs endemic to Madagascar, showing a large variation in morphology and ecological specialization that parallels their phylogenetic diversification. Among them, the genus Blommersia comprises several small species of small to miniature frogs, two of which occur in syntopy on the Comorian archipelago, which was colonized by their ancestor several millions of years ago in an event of transoceanic dispersal from Madagascar. They have evolved in isolation, which has supposed an evolutionary experiment of morphological and genetic divergence without competition. In mantellids, as well as in other amphibians, body size is correlated with dispersal capabilities and these may have allowed the colonization of new habitats in parallel to morphological divergence. Consequently, we hypothesized that variation in the Blommersia musculoskeletal anatomy implicated in locomotor performance would reflect potential differences between species in accordance to their diversification into different ecological niches and lifestyles. To tackle this question we focused on one of the main components of the anuran locomotor system: the pelvis. We compared the pelvic shape of seven Blommersia species, with special emphasis on the Comorian sister species pair and their Malagasy sister taxon. In addition, we mapped for the first time the insertion sites of the musculature on the Blommersia pelvis by means of a customized contrast staining technique prior to CT-scanning. Morphological distances resulting from the pelvic shape comparison between species correlated to a high extent with their 16S phylogenetic distances. In accordance, we discuss the observed patterns of pelvic shape variation and their relationship with size variation in the context of pelvic musculoskeletal architecture evolution in anurans and its potential interactions with locomotor function in the Blommersia genus.