Hanging Bears from Phylogenetic Trees: Investigating Patterns of Macroevolution

Phylogenetic information of the family Ursidae is well resolved and readily available for investigating macroevolutionary questions. Using complete phylogenies of the ursids and related terrestrial carnivores, I investigate whether patterns of body size and life history evolution in bears differ from other carnivores with respect to cladogenesis, species richness, and overall phyletic trends. Large body size in bears is not related to their phylogenetic history, in contrast to most other carnivore taxa; this may relate to bears' relatively recent evolutionary history or their large body size, which is flexible for utilizing low-quality foods, thus buffering environmental change. Also, rates of body size evolution in bears are average or perhaps slightly slower than other carnivores. Certain life history traits (birth weight, age eyes open, inter-birth interval, longevity) are very different in bears relative to other carnivores, even after accounting for body size and phylogeny. In general, large body size, flexibility in phyletic change in size, and slow life histories of ursids may be an effective evolutionary strategy for dealing with recent environmental stresses.