Fig. 6

Relative occurrence of symbionts in I. ricinus nymphs from 19 forest sites coloured by their longitude. Percent of variance explained by each PC: A PC1 (56%) and PC2 (23%). B PC1 (69%) and PC2 (17%). a Relative occurrence of vertically transmitted symbionts such as R. helvetica, M. mitochondrii, S. ixodetis, and Rickettsiella spp. b Relative occurrence of horizontally transmitted pathogens such as A. phagocytophilum, B. afzelii, B. garinii and B. valaisiana (combined), and N. mikurensis. Tick populations from the forest sites situated close to each other (see Fig. 5) clearly share a similar composition of vertically transmitted symbionts but not horizontally transmitted pathogens. Transparent boxes show haplotype numbers, which correspond to symbiont combinations in individual ticks, for example in panel a, the forest sites from the centre of the Netherlands are dominated by nymphs infected only with M. mitochondrii (h08) or with none of the symbionts (h00). Please note the different scales of axes between the two figures. A full description of each haplotype is provided in Additional file 4: Table S9