Using metabarcoding to assess the diversity and composition of pollen collected by the sunflower specialists Melissodes agilis and M. trinodis (Apidae: Eucerini) in an urban and agricultural habitat in North Dakota, USA

Successful production of cultivated sunflower ( Helianthus annuus , Asteraceae) depends on wild and managed bee pollination. Of special importance are the oligolectic bees Melissodes agilis and M. trinodis , which are among the most frequent sunflower visitors and have been shown to increase seed yield, providing significant economic benefits to sunflower production. In this study, we used pollen metabarcoding (two barcodes, ITS2 and trnL) to identify non- Helianthus plants visited by female M. agilis and M. trinodis and to determine whether pollen diversity and composition varied by year, bee species, and site. We collected pollen from 112 bees in two locations in North Dakota (agricultural and urban) during 2019 and 2020. Our results show that both species foraged mostly on sunflowers but also visit other Asteraceae and plants from other families like Fabaceae and Poaceae. ITS2 identified plants representing 36 genera and 17 families, while trnL identified 31 genera within 9 families. The two barcode regions shared 22 genera (61–71% overlap), but each recovered unique taxa, demonstrating the value of combining markers to characterize bee pollen loads. Pollen richness and diversity differed by year (ITS2 and trnL) and site (ITS2 only), but not by bee species. Pollen composition differed by year, site, and bee species for both ITS2 and trnL. Identifying the non- Helianthus floral resources used by Melissodes may help guide the management of field margins and other surrounding vegetation to support wild pollinator populations.