Phylogeny and evolution of floral choices in bees of the tribe Emphorini (Hymenoptera: Apidae)

Bees, like other herbivorous insects, exhibit a wide spectrum of dietary preferences, ranging from broad generalists that collect pollen from many plant families, to narrow specialists that visit a few species. The tribe Emphorini (Hymenoptera: Apidae) includes diverse host-plant specialists, making them ideal candidates for understanding the evolutionary patterns of host-plant use in bees.   Emphorines are restricted to the Western Hemisphere; the tribe comprises 107 described species in 9 genera, being more diverse in arid regions of South America.

The goal of this project is to understand the evolutionary patterns of floral choices in Emphorini, by reconstructing the phylogeny of the group based on ultra conserved elements and recording their preferred host plants.  We have examined specimens from 12 collections in the United States, Mexico, Argentina and Brazil. Based on these visits, we have sampled specimens of 78 species, representatives of all genera. Additionally, to determine the floral associations, we are collecting pollen samples from scopal loads of museum specimens and identifying them to family level based on morphology. By using model-based ancestral state reconstruction methods, we have been able to identify the host shifts that have occurred throughout the evolution of the group. Our analyses recovered all the genera as monophyletic groups. Furthermore, we recovered Malvaceae as the preferred host plant for the most recent common ancestor of Emphorini. We found that Convolvulaceae is an important resource for the tribe, and preference for this family has evolved repeatedly. We are also determining whether diversification is associated with host shifts.