Bumble bees (Apidae: Bombus) through the ages: Historical biogeography and the evolution of color diversity.

The ∼250 species of bumble bees are recognized for their pollination services and are model taxa for the study of foraging ecology and social behavior. In this thesis I utilize a comprehensive species-level phylogeny of the bumble bees of the world to address several evolutionary questions.;In Chapter 1, I use the phylogeny to infer historical biogeographic patterns, divergence times, and diversification patterns in the bumble bees. These analyses indicate that extant bumble bees arose around the Eocene-Oligocene boundary and underwent several intercontinental dispersal and diversification events that correspond with key global events.;Color patterning in bumble bees has very little phylogenetic signal. This is partly the result of convergence in color pattern onto regional Mullerian mimicry complexes. To examine how Mullerian mimicry is evolving in bumble bees, in Chapter 2 I use phylogenetic data to assess color pattern evolution across three comimetic species, B. trifasciatus, B. haemorrhoidalis and B. breviceps, that adhere to ∼14 mimicry complexes in Southeast Asia. In these data color pattern variation exceeds mitochondrial variation and, therefore, is either evolving very rapidly, or cannot be reliably traced with mitochondrial phylogenies. Furthermore, this study reveals that B. trifasciatus is likely a complex of several species.;The rapid rate of color evolution begs the question of the complexity of genetic regulation of color. In Chapter 3, I approach this question by characterizing the pigments responsible for coloration across bumble bees. Orange and black pigments in bumble bees are inferred to be melanins. The yellow pigment, which is shared by species across the bumble bee phylogeny, is rare to nature.;In Chapter 4, I assess mitochondrial 16S sequence divergences between disputed taxa and their potential conspecifics as an indicator of species status. The results suggest recent species lists are likely a conservative measure of the number