Native bees are the largest contributors to animal-mediated pollination, and reports of their decline have prompted studies of bee communities and the implementation of land-use practices that are assumed to benefit bee abundance and diversity. Many studies focus on taxonomic diversity and relative abundances, but these metrics do not directly take into account the functional roles of organisms in an ecosystem. In this study, bee genera were categorized into guilds by nesting habitat and the focus was placed on nesting guild diversity and relative abundances. Specifically, we hypothesized that urban sites where sustainable land-use practices were implemented will have higher nesting guild diversities than other urban sites, and that the former would have nesting guild diversities comparable to rural sites. Sustainable land-use practices were employed at two of our six study sites and included native plantings, no-mow areas, and limited use of chemicals. Bees were collected biweekly using pan traps and sweep netting from April to July of 2016 and 2017. Bees were preserved and identified to genus and nesting guild. Sites were classified as urban or rural based on percent impervious land cover using ArcGIS.
Results/Conclusions
Over the two sampling seasons a total of 3,264 individual bees were collected, identified, and classified into nesting guilds for analyses. Urban sites employing sustainable land-use practices had nesting guild diversities comparable to those of the rural sites (p=0.9051, a priori contrast), while the urban site with no sustainable land-use practices exhibited lower diversity in the analogous comparison (p=0.0002, a priori contrast). These results suggest that sustainable land-use may support bee community functional diversity. Bee communities at all sites were dominated by ground-nesting bees, indicating that southeastern Massachusetts supports a large community of this nesting guild. Two sites displayed low relative abundance while still exhibiting relatively high guild diversities, indicating that land-use practices affect total abundance and diversity differently. The overall implication of this study is that sustainable land-use practices, such as increasing the amount of native plants in an urbanized environment, may positively impact the community of bees in urban areas, thus strengthening the availability of natural pollination services. We would like to note that our conclusions should be interpreted in the context of a limited number of urban and rural sites, and that future work is planned to increase the number and variety of study sites.