Land-use change alters specialist bee diet and drives body size declines

Abstract

Context: Land-use change can cause decreases in plant abundance and richness and the replacement of wild plants with domesticated plants. Changes in plant community composition disrupt mutualistic plant-pollinator interactions with ecological consequences for plants and pollinators, and especially for specialists that rely on certain plants. Objectives: We assessed the effects of land-use change and subsequent shifts in plant communities on resource collection and body size for a bee pollinator, Habropoda laboriosa, a purported specialist of blueberries and related Ericaceae plants. Methods: We collected Habropoda laboriosa across a gradient of land use in north-central Florida including agricultural, natural, and urban habitats. We assessed landcover and floral community composition at each site and related these to bee body size (intertegular distance) and resource use (proportion host plant pollen and pollen diversity collected). Results: Host plant pollen collection and bee body size generally responded similarly to the landscape, both increasing with habitats containing host plants (blueberry farms and natural habitat) but decreasing with urban development. However, host pollen collection and bee body size responded in opposite ways to overall cropland in the landscape, with cropland negatively affecting body size despite positively affecting host pollen collection, indicating other factors associated with cropland might drive declines in bee body size. Conclusions: Land-use change can adversely affect bee diet and body size, and changes in diet likely contribute to changes in body size over time. Specialists are particularly at risk for negative impacts of land-use change due to their inability to shift plant hosts.