Use of genetic markers to quantify bumblebee foraging range and nest density.

Bumblebees (Hymenoptera: Apidae) are important pollinators of crops and wildflowers, but many species have suffered dramatic declines in recent decades. Strategies for their conservation require knowledge of their foraging range and nesting density, both of which are poorly understood. Previous studies have mainly focussed on the cosmopolitan bumblebee speciesBombus terrestris, and implicitly assume this to be representative of other species. Here we use a landscape-scale microsatellite study to estimate the foraging range and nesting density of two ecologically dissimilar species,B. terrestrisandB. pascuorum. Workers were sampled along a 10 km linear transect and 8–9 polymorphic microsatellite markers used to identify putative sisters. We provide the first published estimates of the number of colonies using a circle of radius 50 m in an agricultural landscape: 20.4 forB. terrestrisand 54.7 forB. pascuorum. Estimates of nest density differed significantly between the two species: 13 km−2 forB. terrestrisand 193 km−2 forB. pascuorum. Foraging ranges also differed substantially, withB. pascuorumforaging over distances less than 312 m andB. terrestrisless than 625 m. Clearly bumblebee species differ greatly in fundamental aspects of their ecology. This has significant implications for the development of conservation strategies for rare bumblebees and isolated plant populations, for the management of bumblebees as pollinators, and for predicting patterns of gene flow from genetically modified plants. [ABSTRACT FROM AUTHOR]