Population genetics statistics
For each locality in Europe, North Africa, and western Asia from which ≥10 winter moth individuals were collected, standard population genetic statistics were estimated from the microsatellite genotypes scores, using GenoDive (Meirmans & Van Tienderen, 2004). In the introduced region, we prioritized sampling a small number of individuals from a large number of locations in each region to obtain a broader representation of genetic diversity (see Suarez & Tsutsui, 2008). Null-allele frequencies for each locus were estimated using Dempsters EM method as implemented in GenePop (Raymond & Rousset, 1995; Rousset, 2008).