Winners and losers of climate change for the genus Merodon (Diptera: Syrphidae) across the Balkan Peninsula

The implementation of species distribution models on the research of species response to climate change has increased due to the growing vulnerability and extinction rates of various taxa. Reported declines of pollinator population sizes and diversity due to global changes may negatively affect the services they provide. Considering the importance of hoverflies as pollinators, we predict the climate change effect on the potential distribution range of selected species of the genus Merodon Meigen, 1803. We used two climate models (ECHAM5, HadCM3) and three climate change scenarios (optimistic, modest, pessimistic), under two time frames (2050 and 2080). We predicted the species spatial distribution as well as the species richness and the percentage turnover for two extreme dispersal hypotheses (limited, unlimited). The analysis was implemented using an ensemble forecasting modelling approach. Species adapted to higher altitudes (i.e. with lower temperature requirements) and/or latitudes were predicted to be more vulnerable to climate change vs. species able to tolerate a wider range of temperatures, by losing a higher percentage of climatically suitable area. Significant differences in distribution ranges were found between mountainous and the remaining species groups each one considered separately (viz. climate-generalists, Mediterranean, and east Mediterranean). Southern Balkans were predicted to experience a preservation of species assemblage across all climate change models, scenarios and dispersal assumptions, while the central and northwestern parts were predicted to be subject to an increased change of their species composition. We emphasize the importance of forecasting distribution shifts of a high number of species for the development of conservation strategies. Furthermore, due to the dependence of Merodon fly larvae on geophytes, we highlight the necessity of incorporating biotic interactions to model the potential distribution range shifts of these hoverfly species.