The Evolutionary History Of The Cleptoparasitic Bee Genus Nomada With An Emphasis On The Species Of Eastern North America

Approximately 12% of all bee species found in North America are brood parasitic. Of the different genera of cleptoparasitic bees, the most diverse and taxonomically challenging is the genus Nomada, which has approximately 800 species and is found on every continent except Antarctica. Little is known regarding Nomada biology, evolution, and population dynamics and further complicating studying Nomada is inconsistency in species concepts due to variation within and between species and the lack of updated taxonomic tools needed to identify species. This dissertation aims to address gaps pertaining to the evolutionary history, biogeography, and population dynamics of Nomada at both a global and North American level. The first global phylogeny and biogeography for the genus is presented here. Nomada was found to have a Holarctic origin around 65 million years ago and subsequently dispersed into the southern hemisphere at least three times while also dispersing throughout the Nearctic and Palearctic multiple times over various land bridges. To explore phylogeographic patterns and population genetic structure and diversity, the North American endemic species Nomada articulata was used as a model, a first for a cleptoparasitic bee. It is suggested that the Wisconsinan glaciation influenced N. articulata populations by dividing the species along an east-west gradient but over time, these populations dispersed, creating a single panmictic population that persists to the present. Furthermore, N. articulata is suggested to be a species complex with two possible new and unknown species in the southern United States. Lastly, newly updated keys are provided with the aim to help remedy the lack of updated species level keys for the genus in eastern North America. As a result, fully illustrated keys are provided for five of the seven Nomada species groups found in eastern Canada and the United States covering male and female characters for 15 different species. Additionally, one new synonymy is presented and updated information pertaining to the biology, evolution, and taxonomy is included. The research presented here provides an important first step towards understanding the evolution and diversification of Nomada and how, more broadly, cleptoparasitic bees became one of the most successful groups of bees.