Geographical range of the clade P. ridibundus/kurtmuelleri, haplotype network, distribution of detected lineages, and their haplotypes. For the detailed phylogeographic structure of kurtmuelleri haplotypes see Fig. S2. Symbol sizes in the haplotype network reflect sequence frequencies. Small black circles are missing node haplotypes, each line connecting two haplotypes corresponds to one mutation step. An uncertain contact zone between detected lineages/haplotypes is indicated by question marks. The black arrow represents the affiliation of the introduced population of the P. ridibundus/kurtmuelleri clade in southern Italy based on 517 bp only (MK116532). The colour scheme of haplotype networks and species ranges corresponds with the one used in PCAs (Fig. 1) and the molecular phylogeny (Fig. S1).