Insects face a major threat: In recent years, studies around the globe have reported huge declines not
only in diversity but also in terms of biomass. Among the main drivers for this substantial insect
loss are man-made, globally distributed pollutants. Some of these harmful substances, so called
persistent organic pollutants (POPs), are traceable over decades even far away from their
original source and therefore are of great concern. Atmospherically carried POPs get primarily
deposited through precipitation. Mountainous regions are characterized by particularly high
precipitation rates, resulting in a high deposition of POPs transported over long distances.
Nevertheless, only a few field studies have yet addressed the toxicological effects of POPs on the
health state and developmental integrity of alpine organisms. Here, the local accumulation of
atmospherically measured POPs and mercury was assessed in two bumblebee species occurring
above the tree line at Zugspitze (Germany) and at Hoher Sonnblick (Austria): Bombus wurflenii
represents a typical species of high-altitude habitats, while B. pratorum displays a ubiquitous
distribution across all altitudinal levels. We detected nearly half of all 77 persistent pollutants tested,
as well as mercury, in all bumblebee samples. By means of population genetics we were able to
disentangle genetic factors, like inbreeding, and environmental stressors affecting the two
bumblebee species, as both stressors are potential fitness constraints. Coupled with the results from
geometric morphometrics, we could confirm environmentally induced phenotypic changes in
bumblebee wings: We found, with few exceptions, highly positive correlations for POPs or mercury
and fluctuating asymmetry in the wing shape of B. wurflenii. In contrast, B. pratorum was less
responsive to the pollution, presumably due to different strategies in feeding and nesting behavior.
These findings emphasize the importance of species-specific chemical analyses to relate pollution
levels to fitness proxies. In the context of the rapidly progressing global change, there is an urgent
need to find a way to better protect and conserve alpine biodiversity across national borders.
