Morphological evolution of the skull in fossorial lineages of Gymnophthalmidae (Squamata)

Abstract

The evolution of similar body forms through independent evolutionary processes confirms the expected association between environment and morphology during the evolutionary history of biological lineages. A good example of ecological transition involving similar morphological variations in Tetrapoda is the evolution of fossoriality, habitat usage in which movement and daily activities are performed in the underground and frequently associated with elongate and limbless species. Fossoriality evolved independently many times within vertebrates, and the frequency of its independent origins is particularly evident in Squamata (lizards, snakes and amphisbaenians). The skull, as a complex and functionally integrative structure, has a fundamental role to the burrowing of these animals in the ground. Although the many studies concerning the modularity of the skull, it remains unclear whether morphological similarities of the skull of different fossorial lineages might have been stablished through distinct modifications of the different components of its structure. The following research project proposes to investigate the evolution of the skull morphology in Gymnophthalmidae (Squamata) focusing on the independent origins of fossoriality in two lineages of the clade. Analysis of the head contour variation in 25 species of gymnophthalmid lizards using geometric morphometry will be used to test the hypothesis that the skull shape evolved in association with fossoriality but through different modifications of the distinct elements that compose the skull in these two independent lineages. From the results achieved in this more taxonomically abrangent analysis it will be further evaluated in detail the osteological elements of the skull through CT-scan images of a smaller sample composed of representative species of the different morphologies previously identified. The integrative approach of different evolutionary study fields that characterizes this research project will contribute to the understanding of the processes involved with the origins of the phenotypic diversity and the adaptive convergences during the establishment of the head morphology in fossorial lineages. (AU)