Pollen specialisation of native bees in Dunedin

Solitary bees (Hymenoptera: Insecta) greatly depend on pollen and nectar as they provide essential nutrients for growth and development. Unlike social bees, such as bumblebees and honeybees, solitary bees build their nests and forage for food independently. The quality of pollen and nectar can affect the foraging choices of bees. Because they forage individually, they should seek high quality floral sources to meet their nutritional demands – low floral availability can reduce the pollen and nectar quality, negatively affecting solitary bees’ health and reproduction success. By analysing their pollen diets compared to the available sources of pollen and nectar, we can understand how floral availability could affect the foraging choices of solitary bees. Throughout January 2023, we looked at native bee species in the genera <i>Lasioglossum</i> (Halictidae) and <i>Leioproctus</i> (Colletidae) at four urban nesting sites in Dunedin, New Zealand. We caught bees returning to their nests for pollen analysis and conducted floral surveys of the local area. Even though our research was limited to a single month during summer, we found that <i>L. fulvescens</i> had a more specialised pollen diet than other <i>Leioproctu</i>s species (<i>L. pekanui</i>, <i>L. imatatus</i>, <i>L. huwakiwi</i>) or <i>Lasioglossum sordidum.</i> <i>Leioproctus. fulvescens</i> only collected Asteraceae pollen in our study, whereas both <i>L. sordidum</i> and other <i>Leioproctus</i> species collected multiple floral species. <i>Lasioglossum sordidum</i> mostly collected Ranunculaceae pollen, while the other <i>Leioproctus</i> species mostly collected <i>Veronica</i> (Plantaginaceae) pollen. There was no clear relationship between floral preferences of native bee populations and floral availability within 70 m of their nesting sites. These results contribute to understanding the pollen diets of these native bee species, but more extensive research is needed to understand optimal floral resources for native solitary bees in New Zealand.