Meeting Abstract
Most fossorial mammals converge upon similar morphologies: a slender body shape, powerful limbs, and a tapered skull to assist with movement through the substrate. Convergence in these morphologies among fossorial mammals suggests strong selective pressures for function. Phenotypic integration (degree of covariation among traits) can affect the ability of structures to respond to selection. Here we examine the link between integration and skull morphology in ambulatory and burrowing talpids. We used geometric morphometrics to characterize talpid skull shape and constructed a time-calibrated tree using previously published data. We then tested a series of evolutionary models to understand the role of selection in patterning skull shape. Talpid skull shape evolution fit a two-peak Ornstein-Uhlenbeck model with selection favouring optima for fossorial (e.g., Talpa) and non-fossorial (e.g., Uropsilus) morphologies. We then investigated differences in the level of integration and disparity between these two burrowing behaviours. We found the skulls of highly fossorial talpids occupy different regions of morphospace than those with low levels of fossorial behaviour. We also found that fossorial talpids exhibited high levels of morphological integration whereby the rostrum and braincase regions covary tightly, while ambulatory talpids were more modular with rostrum and braincase regions that vary independently. However, ambulatory and fossorial talpids exhibited equivalent levels of disparity. Despite their high skull integration, fossorial moles have diversified quickly, and exhibit a worldwide distribution despite their specialized niche.
