Integrative morphology in Cycloramphus: uncovering modularity and ecology
The morphology of complex three-dimensional structures such as the skull can be mediated through the interaction between development and function of the subsets that compose them. It is an important consequence of genetic effects acting on phenotypic variation and responsible for greater or lesser integration between specific bone groups. Within the formed groups, the phenotype tends to be more strongly correlated as compared to bones from different groups. This concept, known as morphological modularity, can act as a limiting factor in the evolution of structural form and imply evolutionary trends for organisms as a whole. Such evolutionary trends and constraints can play a central role in the diversification of taxonomic groups that exhibit complex life cycles and remarkable ecomorphology. Such is the case with Cycloramphidae, a family of anuran amphibians notorious for their varying degrees of independence from the aquatic environment for reproduction and larval development. In addition, adult morphological variation is consistent to habitat occupation, ranging from saxicolous to semifossorial. The phylogenetic relationships of the family also draws attention to the ecomorphological diversity. Cycloramphidae have been recovered in Neoaustrorana, with families in which torrential (e.g. Hylodidae), terrestrial (e.g. Batrachylidae) and larval endotrophic (e.g. Alsodidae) habits occur; Neoaustrorana, in turn, was recovered in a clade recently named Ceratophryoidea, along with families in which aquatic habit occurs (e.g., Telmatobiidae), Neomelia (e.g., Rhinodermatidae), and larval carnivory (e.g., Ceratophryidae). This work aimed to discuss the evolution of shape and modularity in Cycloramphidae skulls in light of the ecomorphological diversity found in Ceratophryoidea. Due to the poor taxonomic representation of the clade in the Anuran phylogenies, it was first necessary to elaborate a phylogeny (Bayesian based on total evidence, 226 morphological characters and 6696 base pairs spanning mitochondrial and nuclear genes). In this context, I have studied the morphological integration, the phylomorphic space of the families involved and the differences of the ecomorphological groups they constitute, considering both adult and larval habits.