Combining citizen science, bioclimatic envelope models and observed habitat preferences to determine the distribution of an inconspicuous, recently detected introduced bee (Halictus smaragdulus Vachal Hymenoptera: Halictidae) in Australia

Introduced bees may compete with native fauna, spread parasites or pathogens to commercial bee hives, or increase the fecundity of introduced weeds. Therefore, the recent detection of Halictus smaragdulus, native to the western Palaearctic, in the Hunter Valley region of New South Wales (NSW, Australia) is cause for concern. However, it is currently difficult to justify control measures, as there is little known on its ecology, impacts and distribution. Determining the current distribution is fundamental to managing introduced species, yet this is difficult with inconspicuous species such as H. smaragdulus, especially as recent introductions are often found in low densities. We demonstrated how a combination of approaches could be used to improve the identification of occupied locations in NSW, including bioclimatic envelope models, proximity to known populations, and observed habitat preferences. Members of the public were also trained to collect specimens and improve overall survey efficiency. Bees were collected using pan traps and sweep netting. H. smaragdulus was detected at 44 new locations, extending the known distribution from ~1,250 to 46,800 km2. While bioclimatic envelope models helped guide survey locations, species detectability was higher when observed habitat preferences and proximity to known populations were also considered. We also demonstrated that with training via the internet and appropriate procedures for returning specimens in the mail, members of the public could successfully collect this small and inconspicuous invertebrate, with potential applications for other similar species.