Fig. 1

Map showing the approximate location of Ensis siliqua localities analyzed in Ireland: Strandford Lough (Str), Tyrella (Tyr) and Skerries (Ske); Spain: Celeiro (Cel), Fisterra (Fis) and Barra de Cangas (Bar); and Portugal: Aveiro (Ave), Setúbal (Set) and Olhão (Olh)