Invasive and native bumblebee abundance along a latitudinal gradient within Argentina and Chile, 2019-2020

Fieldworkers recorded a count of the abundance of bumblebee species observed during a transect trail walk. The length of the walk varied on a site-by-site basis depending on local conditions and site size, however, the length of the transect and the time taken to walk it were recorded. Bumblebees were identified in the field by trained individuals to the level of species, but explicitly focusing on Bombus terrestris, B. ruderatus and the native species B. dahlbomii. Collection of individuals for identification is not typically needed but was undertaken where required allowing for subsequent lab-based confirmation. Bee abundance is summed across the transects for each species and each sampling date for a site.

Site location (Latitude and Longitude) as well as the length of the walked transect was determined using the smart phone app Locus Map (https://www.locusmap.eu/) while the duration of the transect walk was timed on a stopwatch.

All field workers were either experts with a long track record of bumblebee identification or underwent extensive training. In contrast to bumblebee assemblages in other parts of the world, which are typically more diverse and contain potentially more cryptic species, those monitored in Argentina and Chile are species poor reducing the potential for errors. Questionable specimens were collected for subsequent identification under laboratory conditions. Data was collected in the field using pre-prepared data sheets. Data sheets were checked both visually and following data entry into digital format by confirming where outlier abundances (>2SD from mean) were found that these were consistent with raw field data sheets. Individuals performing each sampling transect were recorded, allowing the potential for retrospective exclusion of data points if required.