The expected and observed host range of the four ecotypes were calculated for the European samples (All) and Dutch and Belgium samples (Part). Observed: observed number of distinct host species. Expected: expected number of distinct host species given the sample size. Bold italic numerals indicate p-value < 0.025, hence observed host-species richness is significantly less than expectation from the ecotype I. Expected species richness and its p-value were computed using EstimateS (Version 9, R. K. Colwell, http://purl.oclc.org/estimates).