(2nd Place) Phylogeography of the parasitic bee Triepeolus remigatus (Hymenoptera: Apidae) and the effect of its host evolutionary history

The evolution of parasitic lineages is typically associated with the evolutionary history of their hosts. Parasitic or cuckoo bees exploit resources from pollen-collecting bees, but it is unknown to what extent cuckoo and pollinator bees coevolve. This project investigated the phylogeographic patterns of a parasitic bee and the degree of concordance with its host's evolutionary patterns. Triepeolus remigatus (Hymenoptera: Apidae) is a parasite of the squash bee Xenoglossa (Peponapis) pruinosa (Hymenoptera: Apidae), a specialist pollinator of squash and pumpkins, that has experienced a recent geographic expansion from Mexico into eastern North America, following the cultivation of Cucurbita plants. This expansion has resulted in phylogeographic structure across the host distribution. Both species occur across continental North America, and we hypothesize that T. remigatus has mirrored the phylogeographic patterns of its host as a result of a similar geographic expansion. To test this hypothesis, we generated Ultraconserved Elements genomic data from recent and historical museum specimens collected across the distribution of T. remigatus resulting in a dataset of 158 individuals. Phylogeographic analyses show that T. remigatus individuals cluster in clades that correspond to different North American biomes, with few differences between individuals present in the temperate grasslands and eastern forests of the Midwest, northeast, and southeast US, but a deep phylogeographic break in individuals from the desertic areas of southwestern US and tropical dry forests of western Mexico. This pattern is similar to results found for X. pruinosa in previous studies, indicating a possible correspondence between the histories of the two species.