Adaptive introgression in invasive slugs

Theoretical work predicts that during a species invasion, genes from a native species often move into the genome of the invasive species, potentially facilitating its adaptation to local environmental conditions. Such asymmetric introgression has been confirmed in diverse taxa such as plants, fish, and even humans. It is yet unclear if introgression is selectively adaptive facilitating invasiveness, or if it is neutral reflecting demographic history. We provide insights into this question by studying the divergence and gene flow of Arion slugs. Within the last 100 years, likely facilitated by changes in climate and land use, the slug species Arion vulgaris expanded from southwestern France to all of Europe, and more recently to North America, becoming an important plague in agriculture. In this process, this invasive species hybridized with several native slug species, leading to their destruction across most of their range.