Sampling Bees (Hymenoptera: Apiformes) for Pollinator Community Studies: Pitfalls of Pan-trapping

Abstract

With the growing interest in pollinator conservation, a need has emerged for a simple, unbiased method to reliably sample local bee faunas. One method, pan-trapping, has increased in popularity without critical evaluation of its efficacy and biases. We compared traditional net collecting at flowers and pan trapping concurrently, sampling the local bee fauna of the dominant desert shrub, creosote bush (Larrea tridentata) growing at the Silver bell site of the International Biosphere Program (IBP) nw of Tucson Arizona. Pan-traps on the ground yielded a faunal sample depauperate in many of the more common native bee species on creosote bush, particularly its floral specialists. This pan-trap sample also corre sponded poorly with the previous four years' faunal samples at this site, with pairs of neigh boring net-sampled sites throughout the Southwest, and with all pairs of bee samples from Larrea across the Upper Sonoran desert. The likely causes of this disparity and the utility of pan trapping for bees in faunal and community studies is discussed.