Phylogeography of the cleptoparasitic bee Nomada articulata (Smith, 1854)

The genus Nomada is considered the largest and most diverse of the cleptoparasitic bees, however, very little is known about their population dynamics. Studying Nomada populations can be difficult due to their solitary and parasitic nature; often only occurring in small numbers and collected in passive traps. Despite their obscurity, some Nomada species are relatively common such that natural history and host species interactions are known. The spring flying species Nomada articulata (Smith, 1854) is a frequent nest parasite of Agapostemon virescens (Fabricius, 1775) and Agapostemon sericeus (Forster, 1771) and is found throughout North America. Owing to its large geographic range and common status, we selected N. articulata as a model to examine the phylogeography of this widespread species. Using Ultraconserved elements (UCEs) we 1) detect the genetic variation among N. articulata populations across it range, 2) identify population structure across landscapes, and 3) determine cryptic species diversity using combined morphological and genetic datasets. Both UCE and mitochondrial trees for 75 N. articulata individuals were analyzed, each representing one of four regions in the US or Canada: South, West, Midwest, Northeast. These data suggests that N. articulata may be a species complex with distinct genetic diversity in southern populations. This is the first phylogeography for a North American Nomada species and provides a foundation for understanding how cleptoparasitic bee populations have responded to host ranges and environmental changes over time.