HOLLIDAY, Jill A.; Florida State University: Character evolution in Carnivora: specialization, stasis, and directional bias

In mammalian carnivores, hypercarnivory is a meat-specialist dietary niche characterized morphologically by relative elongation of the carnassial blade, relative reduction of the post-carnassial dentition, and relative shortening of the rostrum. Hypercarnivory has evolved numerous times within the order Carnivora, including certain members of such disparate lineages as felids, viverrids, hyaenids, canids, mustelids and nimravids. This repeated evolution of the hypercarnivore phenotype provides natural replicates for comparative study. Using sister group comparisons, I show that specialization to hypercarnivory limits subsequent morphological diversification. Furthermore, once taxa achieve this specialist phenotype, they do not appear able to reverse to a less-specialized morphology or to move to alternative niches; rather, change is generally in a forward direction (towards increasing specialization). In order to understand and explain these limitations, I examine mechanisms that could generate the observed patterns. In particular, I test for the presence of a directional bias in morphological character change as lineages move towards hypercarnivory, comparing rates of forward change, reversal, and stasis in specialist vs. non-specialist lineages.