Food plants and foraging distances for the native bee Lasioglossum sordidum in Christchurch Botanic Gardens

With concerns about declines in pollinating bee species worldwide, there is renewed interest in solitary native bee species and their role in pollination services. We studied the foraging preferences and foraging distances of Lasioglossum sordidum (Halictidae), New Zealand’s smallest solitary bee, in urban Christchurch. Lasioglossum sordidum were abundant within the Christchurch Botanic Gardens. Pollen samples taken from 40 bees at each of two nest sites were identified using a pollen reference collection from the sites. Bees were collecting pollen from both native and exotic plants. In total, pollen from 23 different plant taxa was found, but 96% came from five taxa: Asteraceae (65%), Hebe spp. (16%), Aesculus spp. (8%), Yucca baccata (3%) and Taraxacum officinale (3%). Individual bees usually specialised in a few pollen types, with 74% of bees having >90% of a single pollen type and a mean of 2.6 pollen types per bee. The minimum flight distances to the nearest sources of each pollen type were typically 70–250 m. These easily overlooked bees may be assisting more in general pollination services given the diversity of plant taxa from which the bees were collecting pollen, the variation from bee to bee in the plant taxa collected, and the sometimes considerable minimum foraging distances exhibited.