Bad company expands in highland areas: Overlapping distribution, floral resources and habitat suggest competition between invasive and native bumblebees

Bumblebees are key pollinators, but their global decline is being driven by factors such as invasive species. Bombus terrestris has invaded many countries, displacing and competing with native bumblebees for resources throughout many different habitats, which causes native populations to decline. In the Chilean highlands, Bombus funebris-a Chilean species under threat-shares its habitat with B. terrestris, suggesting that the two species could be competing for resources (e.g., flowers or habitats) within this ecosystem. However, an information gap in this regard prevents us from proposing conservation measures. Our goals were (1) to assess overlapping distribution between native and invasive Bombus species, (2) to determine any niche overlap in the use of flowers between the two bumblebee species, and (3) to document the predictors that influence their abundance. We conducted a survey in northern Chile between 2017 and 2019 with different latitudinal and altitudinal sampling points to count bumblebees and record their interaction with flowers, both in natural and perturbed habitats. We analyzed their overlapping distribution using the chi-square test and evaluated the use of floral resources and their overlap niche through an interaction network analysis. Predictors and bumblebee abundance were associated with a general linear mixed model. We found the distribution of both bumblebees overlapped by 94.3 %, whereas the overlap niche index (NO) for the common use of flowers was high between B. terrestris and B. funebris (NO = 0.78). The abundance of both bumblebee species was associated with the use of natural scrubland in the highlands. Our results suggest that both species are likely to have a competitive dynamic for floral resources in the high Andean scrubland. As such, we propose implementing an export ban on invasive bumblebee species, coordinating measures between bordering countries, removing any remaining B. terrestris populations, and restoring native flora to attract native pollinators and to provide and manage pollination services in the Chilean highlands.