The relative importance of body size, phylogeny, locomotion, and diet in the evolution of forelimb dexterity in fissiped carnivores (Carnivora)

Using a new rating scale of forelimb dexterity that separates the contribut ion of proximal components (shoulder, upper forelimb, and lower forelimb) f rom distal components (forepaw), we examined the relationship between funct ional demands and phylogeny and forelimb dexterity in 45 species of fissipe d carnivores (Carnivora). Specifically, we examined the effects of body siz e, phylogenetic relatedness, diet (vertebrate predation), and locomotion (a rboreality) on the differential evolution of forelimb dexterity. Regression analyses indicate that, although body size does appear to be positively co rrelated with the dexterity of the proximal components, the inclusion of ph ylogenetic information results in a nonsignificant relationship. Phylogenet ic relatedness was found to account for a significant amount of interspecif ic variation in proximal, distal, and total (proximal + distal) dexterity. When phylogenetic effects were incorporated, arboreality was not significan tly correlated with any of the dexterity scores, but vertebrate predation w as, albeit a negative correlation. The amount of variation in the dexterity of proximal and distal components did, however, differ in magnitude within each significant result. Thus, each component can be differentially affect ed by specific functional demands. By examining the significant association s with diet and phylogeny and mapping the dexterity scores onto the phyloge ny, we also demonstrate that the ancestral degree of forelimb dexterity of both the caniform and feliform lineages was approximately equal to that of the average extant carnivore. Thus, forelimb dexterity has decreased or inc reased within particular lineages, with reductions or elaborations in some species resulting from the invasion of specific niches not occupied by cong eners.