Conclusions
Bumblebees of cold environments in the main European mountains act as sentinels and respond in a similar way to global climate change by shrinking their distribution and shifting uphill in elevation, in spite of having different distributions and life histories. This will likely lead to issues such as habitat loss, reduced surfaces for acquiring resources and finding mates. Furthermore, it is possible that future scenarios will also contribute to the erosion of genetic diversity, as a low genetic diversity has been found in declining bumblebees (Cameron et al. 2011) and also in other high-elevation specialist species (Bauert et al. 1998, Rubidge et al. 2012). This scenario challenges dramatically any conservation effort but attention should be directed towards the dynamic realities of species ranges.
The narrow future ranges and small refugia will lead to conservation issues for cold-adapted bumblebees. However, conservation should take in full consideration the dynamic realities of species ranges over time and that refugium areas may be target of conservation priority considering in situ and ex situ locations. Moreover, a useful tool could be updating the country- and continental-level Red Lists in light of the results presented in this study, and the different responses among mountain ranges highlight the need for regional lists at smaller scales. Furthermore, protecting and keeping high habitat quality and microhabitat diversity in current and in refugium areas will be the first pillar for any reasonable conservation plan. Other future conservation actions could also integrate biogeographical and genetic evidence in order to further tailor the design of conservation priority areas and therefore help outlining specific measures to preserve these species.