EVALUATION OF DISPARITY METRICS FROM MORPHOLOGICAL CHARACTER MATRICES AS PROXIES FOR FUNCTIONAL OVERLAP

Disparity analyses using morphological character matrices are becoming more widespread in paleontological studies. As morphological disparity is commonly used as a proxy for functional roles, these studies seek to infer potential biological interactions between clades from morphological character matrices. Additionally, measures of character saturation from these matrices allow for the comparison of morphological constraints between clades, where early saturation is assumed to reflect stronger constraints. However, most character matrices were initially constructed to infer phylogenetic relationships between taxa and thus tend to rely largely on non-functional characters to limit the effects of convergent evolution. Therefore, the abundance of non-functional characters in morphological character matrices could produce misleading estimates of functional disparity. In this study, we test the degree to which disparity estimates from morphological character matrices reflect functional overlap. Here, we compare pairwise morphological dissimilarity calculated from a character matrix of living and fossil canids with pairwise differences of their associated functionally significant craniodental ratios. We also test to see if the point at which character saturation occurs in each Canidae subfamily corresponds is positively correlated with the area of occupied functional morphospace. We find that pairwise morphological dissimilarity weakly but significantly correlates with functional trait range. In addition, the points at which character saturation occurs within fossil canid subfamilies do not correspond with the area of occupied functional morphospace. Instead, clades characterized by the continued appearance of new characters can still exhibit constrained functional morphospace. Our results highlight the potential limitations of discrete character-taxon matrices for studying the evolutionary impacts of biological interactions and functional constraints, respectively.