Species richness and life-history traits of butterfly communities along an altitudinal gradient in the German Alps

Background/Question/Methods

Life-history traits, the characteristics of species, can help to predict species reactions to climate change. In the next decades elevational range shifts of many species are expected due to progressing global warming. Butterfly species serve as perfect model species in climate change research, because they react sensible to environmental variations and their biology and ecology is well studied. So far, single life-history traits have been mostly investigated for individual species, but we were interested in climate-related variation of multiple life-history traits on community level. Thus, the goal of this study was to determine species richness patterns along an altitudinal gradient in the German Alps and to use these data for life-history trait analyses on the community level. Surveys were conducted at 34 sites in the National Park Berchtesgaden and its surroundings in southeast Bavaria/Germany. Butterfly species were sampled in transect walks along an altitudinal gradient to analyse elevational richness patterns. Community life-history trait calculations were performed using sampled species richness data and species life-history data from published literature. Altitudinal changes of eight life-history traits were analysed by calculating mean values of the traits per community.

Results/Conclusions

We identified a total of 67 butterfly species and collected between 12 and 23 species per site. Butterfly species richness linearly declined with altitude and was halved at 2000m compared to 600m altitude. Fife of the eight analysed life-history traits showed a significant correlation with altitude. Wing length was in average 9 % larger for butterfly communities at higher sites compared to butterfly communities of lower sites. Communities of butterfly species at higher altitude laid on average 68 % more eggs in comparison to butterfly communities at lower altitude. Egg maturation time was 22 % shorter for butterfly communities at elevated sites compared to butterfly communities at lowland sites. Average population density declined with increasing altitude and was 59 % lower for alpine compared to lowland butterfly communities. Further, high altitude butterfly communities had on average smaller distribution ranges in Europe than low altitude butterfly communities. The three remaining life-history traits, generations per year, egg deposition mode, and dispersal capacity showed no significant correlation with altitude. The data provide evidence for significant shifts in the dominance of life-history traits at a community level along altitudinal gradients. In the face of climate change it is very important to comprehend the mechanisms that determine species richness and to take adaptation strategies into account for enhanced conservation measures.