Modelling the spatial abundance distribution of Melanargia galathea in a changing environment

Paganini A. 2016.Modelling the spatial abundance distribution of Melanargia galathea in a changing environment. Master Thesis ETHZ, D-USYS. Supervisors: PD Dr. J. Bolliger, Dr. R. Wüest-Karpati.

This Master thesis assesses and predicts the abundance and spatial distribution of the butterfly Melanargia galathea in Switzerland and Liechtenstein for present and future environmental conditions. The main objective was to explain the spatial pattern of butterfly monitoring observations of M. galathea at 474 locations as function of landscape, distance, relief and climate variables across Switzerland and Liechtenstein. For this, different circular areas around each butterfly observation location were used as surrogates for the movement potential of the species, within which the explanatory variables were calculated. Four statistical models and two different ensemble model approaches were used to project the butterfly abundances spatially explicitly and to analyse the influence of the different models on the predictions. Major results showed that temperature and slope have a strong positive effect on the abundance of M. galathea, while the proportion of buildings should not be over 25% and the annual precipitation total is optimal around 800 mm. Currently, the hotspot of M. galathea abundances are located in the Swiss Alps (Valais, Ticino, Graubünden) and in the Jura Mountains. I used two climate warming scenarios RCP4.5 and RCP8.5). The low warming scenario RCP4.5 (+4°C; -20% precipitation in 2100) has a rather negative effect on the abundances of M. galathea in lower elevations and a rather positive effect in higher elevations. The same is the case with the strong warming scenario RCP8.5 (+6°C; -40% precipitation in 2100), but the positive effect on higher elevations is more distinct. Under warming an expansion of the distribution ranges are observed in the Valais, the northern edge of the Swiss Alps, partly in the Jura Mountains and in the continental High Alps. A range contraction is to expected in Ticino, Graubünden, Swiss Plateau and partly in the Jura Mountains. The comparison of the predicted abundances of M. galathea for the present and under climate change with three land-use scenarios, revealed no influence of these land-use scenarios on the spatial abundance distribution of M. galathea.