EVOLUTION OF DIET SPECIALIZATION IN POISON-DART FROGS (DENDROBATIDAE)

Using the family of poison-dart frogs (Dendrobatidae), this study inve stigates the hypothesis that a trait should evolve to become more spec ialized: i.e., that diets should evolve to become narrower. I propose and then test a specific hypothesis that specialist diets evolved from generalist diets in the Dendrobatidae, by explicitly defining ''speci alist'' in the context of the foraging ecology of these frogs and by f ollowing guidelines for the comparative method proposed by Harvey and PageI. Overall, the genera judged to be more basal in the phylogeny (C olostethus, Epipedobates, Phyllobates) had wider and more generalist d iets, in contrast to taxa higher in the clade (Dendrobates, Minyobates ) which had narrower and more specialist diets. However, some genera ( Phyllobates, Minyobates) did not fit neatly into this sequence, exhibi ting wider and narrower diets, respectively, than expected based on ot her traits. I tentatively conclude that a narrow diet specializing on ants and mites is a derived trait and that a generalist or opportunist ic diet is an ancestral trait in the Dendrobatidae. Moreover, suites o f traits related to diet and foraging suggest that foraging ecology ma y have been a significant force driving radiation of the family at the generic level.