Population-genetic structure of Oswaldocruzia filiformis found in Slovak populations of frogs, based on COI haplotypes presented as a median-joining haplotype network. The sizes of the circles in the network are proportional to the relative frequencies of the haplotypes; small black circles represent missing haplotypes. The vertical lines represent the number of substitutions between individual haplotypes. Different colors represent specific host taxa for O. filiformis according to the legend. The haplotype numbers correspond to those in Figure 1 and Supplementary Table S1.