THE ROLE OF PHYLOGENY IN THE EVOLUTION OF CRANIOMANDIBULAR FUNCTIONAL MORPHOLOGY IN FOSSIL AND EXTANT FELIDS

An important question in evolution is the degree to which phylogeny constrains morphology and function. Here, the role of phylogeny in the evolution of cranial morphology and biomechanics has been investigated in extant and fossil felids, the latter including the enigmatic sabre-toothed cats. First, morphological and biomechanical characters were tested for phylogenetic signals. Second, the biomechanical variance was partitioned into morphometric, phylogenetically structured morphometric, and phylogenetic variances. Third, phylogenetic patterns in morphospace, function space, and univariate character change were visualised through maximum likelihood ancestor reconstructions. Lastly, phylogenetically structured allometric patterns are elucidated.

Results show that morphological and functional characters generally exhibit significant and strong phylogenetic signals. Variance partitioning further confirms that the majority of the functional variance can be explained by phylogeny, although the phylogenetically structured morphometric proportion of variance is small. This indicates that while both morphology and function show strong phylogenetic inertia, they are constrained in different ways. Further, differences in morphological and functional characters among taxa are consistent with phylogenetic distances, or that closely related taxa are more similar than distantly related taxa. Mapping a phylogeny onto morphospace (or function space) also shows clear phylogenetic patterns; most felid clades occupy areas of morphospace proximal to their respective reconstructed ancestors. Phylomorphospace reconstruction also shows a strong phylogenetically structured allometric trend, but medium-sized cats are not evolutionary transitions between the large-sized and small-sized cats. The two subfamilies, Felinae and Machairodontinae seem to follow separate allometric trajectories.