Impacts of land-use change on bee community distributions and ecology

Land conversion, notably for urbanization and agriculture, is increasing on a global scale, yet the impact this will have on natural communities remains uncertain. Even for ecologically and economically important groups such as pollinators, there remain many questions on how land-use change will affect population distributions and interaction relationships. I conducted field work in June-August 2010 and March-September 2011 in East Contra Costa County, California, where residential, agricultural, and natural areas meet at a common interface.

I investigated how land-use context impacts bee community distributions, bee-plant interactions, and pollination services. To discover where bees are flying I sampled bees at 24 sites (8 each within residential, agricultural, and natural land-use types) in open areas through bimonthly pan trapping. I also selected target plants that could be found throughout all sites, and measured pollinator visitation. To test the assumption that more diverse and abundant bee communities are equitable with more pollination services, I measured seed set proportions of these target plants for pollen limitation.

I found that natural areas have the most diverse and abundant bee communities overall, but this pattern changes seasonally and with different ecological bee groups. The most tightly linked interaction networks also occurred in natural areas. Seed set proportions were highest in natural areas, followed by urban, and agricultural. Urban areas have potential to support high bee diversity, but are also the most variable between sites.