On the move: southern range expansion of Italian parti-coloured bats

Climate change is a major driver of biogeographic patterns, prompting species to shift their geographical ranges. Most documented distributional changes by wildlife related to climate change involve poleward expansions or shifts. Here, we document a southward range expansion in the Italian territory by the parti-coloured bat, Vespertilio murinus. Considered as restricted to the Alps, a recent surge in sightings triggered the question of whether these observations represent an expanding local lineage or central European populations crossing the Alps. We employed a multifaceted framework to address this question, coupling genetic sampling, species distribution modelling, and citizen science approaches. By analysing two mitochondrial genes, we revealed that three haplotypes of V. murinus occur in Italy, two of which are unique to the country. Species distribution models predicted the highest range suitability around the Alps and the Apennines, with low suitability in the Po Plain and coastal areas of central and southern Italy. The consistent presence of suitable spots may act as a stepping-stone network for the southward species expansion towards. We present a compelling case for a divergent Italian lineage of the parti-coloured bat featuring a unique ecological response. This study highlights the importance of adopting a replicable approach to identify the genetic and ecological uniqueness of taxa from glacial refugia and disentangle patterns of range expansion under global environmental change.