Bumble bees contribute to North America’s economic success and natural resources as pollinators of crops and wildflowers. In recent years several bumble bee species have declined dramatically, including the rusty patched bumble bee (Bombus affinis), which was placed on the federal endangered species list in 2017. The primary goal of this study is to determine the distribution of B. affinis and another species of concern, B. terricola, in Ohio, USA, and to document their habitat use and food plants. Secondarily, we are investigating how the amount, quality, and distribution of foraging habitat across the landscape affects bumble bee species diversity and abundance. Our results can be used to develop management practices that will help prevent the decline of species that are currently widespread and abundant. In summer 2017, we surveyed bees in 130 wildflower meadows in 46 Ohio counties. At each site, a team of trained observers recorded bee visits to flowers for 1.5 hours and counted all open flowers in a 100m2 area.
Results/Conclusions
We observed 10,078 bumble bees representing eight species, visiting 132 species of flowers. Neither B. affinis nor B. terricola were observed, although their preferred food plants were found growing abundantly. Bombus abundance per 90 minute survey was positively influenced by flower species richness, but not by flower abundance. Regardless of differences in abundance, rarefied bumble bee diversity was higher in early-successional abandoned fields and in planted wildflower meadows than in roadside patches of flowers and old fields. Based on NMDS ordination, Bombus species assemblage was significantly influenced by site flower richness and abundance, and landscape setting. Contrary to expectations, Bombus diversity was negatively correlated with the proportion of forest within a 2km buffer area of a site, and positively correlated with the amount of cropland. Temporally, diversity peaked in June, although plant-bumble bee networks had greater interaction diversity in August. Bumble bees differed by species in their most-visited food plants. Bee yield was not related to the time of day in which a survey took place. In 2018 we will expand our surveying efforts in under-sampled areas of the state. Additionally, we will conduct spring queen surveys to better understand how early-season flower resources may support or limit colony establishment.