Evidence for evolutionary change associated with the recent range expansion of the British butterfly, Polyommatus agestis, in response to climate change

Poleward range expansions are a widespread response to recent climate change and are crucial for many species’ future persistence. However for many species evolutionary change in traits such as colonisation history and habitat preference may be necessary to track environmental change across a fragmented landscape. Understanding the likelihood and speed of such adaptive change has therefore become an important issue in determining the effect of ongoing climate change on extinction rates. We conducted an AFLP-based genome scan across the recently-expanded UK range of the Brown Argus butterfly, Polyommatus (subgenus Aricia) agestis, and used both outlier-based (DFDIST and BayeScan) and association-based (Isolation-By-Adaptation) statistical approaches to identify signatures of evolutionary change associated with range expansion, and shifts in host plant use. We present evidence for (a) little effect of range expansion on neutral genetic structure and (b) strong signatures of selection at ~...