Osteology of the autopodium of Tropiduridae (Squamata: Iguania): modularity, phenotypic integration and microhabitat use

Abstract

In Evolutionary Biology, the concept of phenotypic integration presumes that elements that share developmental pathways or execute interconnected functions would be more integrated within each other than with other structures in the organism. Multicellular organisms can therefore be organized in units or modules, which hold intrinsic functions and structural properties, exhibiting interdependence of genotype-phenotype networks during development. Among tetrapods, the autopodium represents a unique and diversified system regarding morphological and functional aspects, which shares structural similarities among lineages that might be explained by phylogenetic history and ecological convergence. The autopodium is a remarkable structure to investigate the evolution of covariance patterns between osteological elements and specific scenarios of ecological diversification, as the osteological patterns in the autopodium and the occupation of certain ecological niches might elucidate the effects of specific selective pressures acting during the integrated evolution of phenotypic traits in specific lineages. This project for a Master degree aims to test for the occurrence of functional and developmental modules in the autopodium of lizards from the Tropiduridae family (Squamata: Iguania), using analyses based on variance and covariance matrices to evaluate the force of phenotypic integration in osteological elements in the autopodium of species that occupy structurally different environments. Tropiduridae lizards move along an extensive variety of microhabitats in terrestrial environments (rocks, sand, branches and trees), and ecomorphological associations suggest differences in the relative proportions of elements in the autopodium without any change in the ancentral phalangeal formula of this group. Locomotor performance in different environments is associated with specific morphologies of the autopodium, specially when running on the sand. Despite evidence for associations between morphology and locomotor performance in specific microhabitats in Tropiduridae, the autopodium has not been investigated under a perspective applying concepts of modularity and phenotypic integration based on variance and covariance matrices. The investigation of phenotypic integration in this context might elucidade how the lizard autopodium is morpho-functionally structured, fostering inferences related to the developmental mechanisms that may affect the establishment of modules during the Tropiduridae evolutionary history. (AU)