Wild bee responses to land use change: investigating the role of bee body size

Land use change impacts biodiversity through many facets including an alteration of habitat and the resources required to sustain species and populations. Wild bees (Hymenoptera: Apoidea) are essential pollinators for many wild and cultivated flowering plants, and exhibit marked differences in life history traits. The consequences of land use change may therefore affect wild bees differently, but this remains poorly understood for many taxa. Body size is a trait that can vary widely across and within bee species, and has important ramifications for several aspects of bee fitness including foraging range. To better understand wild bee responses to land use change, I focused on bee body size from the scale of the community (interspecific) and within a species (intraspecific). In Chapter 1, I examined tallgrass prairie remnants and restorations across eastern Kansas and found that both types of prairie hosted a similar abundance, diversity, and body size of trap-nesting bees over both study years. The bee community composition differed between prairie types in the first study year but not the second. Regardless of prairie type, bee diversity increased with increasing forb diversity but did not have significant associations with landscape composition. Trap-nesting bee abundance and interspecific body size did not vary in relation to local forb diversity or landscape composition. In Chapter 2, I again used the context of the tallgrass prairie to focus on the response (i.e., total offspring produced, intraspecific body size, and sex ratio) of a single bee species, Heriades carinata, to prairie type, forb diversity, and landscape composition. My results indicate that within this species, foraging mothers provision a greater number albeit smaller size of offspring (both male and female) in prairies with increasing forb diversity. These trends were not extended to the landscape scale, however, indicating that the resources immediately surrounding nest sites may have a greater influence on bees in these sites. In Chapter 3, I extend the question of interspecific bee body size to stingless bee communities collected across a deforestation gradient in Rondônia, Brazil. Stingless bees are diverse and important pollinators in tropical systems, but little is known about how they respond to habitat loss and fragmentation from a trait-based perspective. I found that larger bees were collected more often in areas with less forest and within landscapes that had greater isolation between remaining forest patches, while smaller bees were found in areas with a greater amount of forest and shorter distances between forest patches. In Chapter 4, I find that Africanized honey bees were observed more frequently in open (i.e., deforested) areas but still rely on some amount of forest in the landscape. Taken together, my results suggest that body size differently affects wild bee responses to land use change