SD38: Untangling the impacts of kleptoparasitism on bee health and behavior

Aggregating ground-nesting bees are essential and often understudied pollinators that may be increasingly threatened by anthropogenic change. In this study, we investigated whether parasite load could be an indicator of the health of ground-nesting bee aggregations. Nest parasites (kleptoparasites) often wait at nest aggregations for female hosts to provision their young with pollen before laying their own, faster hatching eggs, on the provision. Kleptoparasites kill the host bee larvae and may also decrease the overall fitness of the aggregation through behavioral changes. To better understand how these kleptoparasites affect the health of ground-nesting bees, we explored how kleptoparasite density impacts chimney bee (Anthophora abupta) behaviors and several indicators of overall aggregation health. We conducted a field study to obtain foundational data such as host behavior, parasite and host density, host body size, pollen quality, and pollen abundance. Using this data, we were able to ask more targeted questions about Monodontomerus mandibularis, the most prevalent kleptoparasite across our surveyed aggregations. We then further explored how M. mandibularis impacts A. abrupta reproductive success with controlled lab experiments and used choice tests to determine their preference for bee hosts. Our study provides information on how host-parasite interactions influence bee health for aggregating bees. Understanding the intricacies of bee health and the impact of nest parasites is paramount for effective conservation pathways.