Pollen samples from a bumble bee (Hymenoptera: Apidae) collection show historic foraging on introduced and native plants in the South Island of New Zealand

Historic pollination networks are important to understand interactions between different plant and pollinator species, as well as to differentiate between causes and consequences of present insect population decline. Natural history collections in museums store biological proxy data, which is used to reconstruct historic pollination networks of bumble bees. Four bumble bee species (Bombus terrestris, B. ruderatus, B. hortorum and B. subterraneus) were introduced to Aotearoa New Zealand in 1885 specifically for pollination purposes. Pollen samples were collected from museum specimens of three of the four NZ species of bumble bee (excluding B. subterraneus) collected between 1954 and 1972 from 56 locations across the South Island, New Zealand. The most common plants identified on all three bumble bee species were Calluna vulgaris (heather), Ulex (gorse), Cytisus (broom), and Trifolium repens (white clover). However, all three bumble bee species also carried pollen from several native plants (e.g. Arthropodium, Weinmannia, Plagianthus, Quintinia, Veronica, Melicytus) and potentially had been involved in the pollination of these species. This study adds new plant species known to be foraged upon by bumble bees in Aotearoa New Zealand. Further studies on pollination networks in New Zealand will help us understand any changes in host plant preferences over time and after the time period covered by this study.