Pairwise estimates of FST (θ: [41]) and mean individual assignment of likelihood (Li→S) of each potential source population (indicated in parentheses) [38] sampled during the southern European introduction and establishment/spread phases.

Criteria for determining population source is lowest FSTand highest Li→S(bold values).*Venezia district**Pordenone district***admixed population of southern Europe (originating from the first populations introduced in Europe.Significant levels of differentiation were found at the intercontinental spatial scale between all southern European and USA populations (FST = 0.06–0.20, P Table 3).Samples from the USA were included as the USA is the known source of WCR in Europe [2].