Using monitoring data gathered by volunteers to predict the potential distribution of the invasive alien bumblebee Bombus terrestris

We explored the use of ecological niche-modeling from data compiled in a participatory program of thousands of volunteer observers to quantitatively evaluate the spatial risk of invasion by the alien species Bombus terrestris. B. terrestris has been commercially introduced to Japan for the pollination of greenhouse tomato crops since 1991. Recently, naturalized populations of this species have spread rapidly, particularly in Hokkaido, northern Japan. Two niche-based models were constructed from independent data sets (presence-absence and presence-only data sets) and were used to validate one another. Both models performed well and indicated that the data compiled by participatory programs were useful for generating predictive models of the potential distribution of this invasive species. The models also revealed that the potential distribution of B. terrestris is negatively related to the proportion of woodland area, which corresponds to the known biology of this species. In contrast, the effect of the number of colonies introduced for tomato pollination (represented by tomato production) did not significantly affect the distribution of B. terrestris, indicating that its spread is now entering a phase of dispersal from established feral populations and that primary dispersal from commercial colonies in greenhouses is no longer a limiting factor for the distribution of this invasive species.