Reduced host-plant specialization is associated with the rapid range expansion of a Mediterranean butterfly

Aim: Species ranges are highly dynamic, shifting in space and time as a result of complex ecological and evolutionary processes. Disentangling the relative contribution of both processes is challenging but of primary importance for forecasting species distributions under climate change. Here, we use the spectacular range expansion (ca. 1,000 km poleward shift within 10 years) of the butterfly Pieris mannii to unravel the factors underlying range dynamics, specifically the role of (i) niche evolution (changes in host-plant preference and acceptance) and (ii) ecological processes (climate change). Location: Provence-Alpes-Côte d’Azur, France; North Rhine-Westphalia, Rhineland-Palatinate and Hesse, Germany. Taxon: Insect and angiosperms. Methods: We employed a combination of (i) common garden experiments, based on replicated populations from the species’ historical and newly established range and host plant species representative for each distribution range, co-occurrence analys...