Figure 2.

Map of Europe showing sampling regions defined by genetic differentiation in the fly Urophora cardui. The parasitoid Eurytoma serratulae was absent on the Jutland peninsula (insert) before 2002 but present elsewhere. Fly populations in Jutland are divided by a genetic transition zone that separates a divergent population in North Jutland (North) from other regional populations. The specific sample locations and sample sizes per location and region are shown in Table 1