The effect of host vicariance and parasite life history on the dispersal of the multi-host ectoparasite, Hyalomma truncatum

Aim: It is predicted that the dispersal and gene flow of ectoparasites with wide host ranges are correlated with the vagilities of their most mobile hosts. To test this, the phylogeographical structure of a widespread generalist tick occurring on large ungulates was determined and compared with previously published host patterns. Location: Africa. Methods: mtDNA cytochrome c oxidase subunit I (COI) sequences were generated for 182 Hyalomma truncatum specimens sampled from 21 Afrotropical localities. A subsample of these was sequenced for the nuclear Histone 3 (H3) and Calreticulin (CRT) regions. Phylogeographical inferences were made by using haplotype networks, a Bayesian analysis of population structure, isolation by distance (IBD) and a Bayesian gene tree. Demographic changes in the populations were determined with Bayesian skyline plots. Results: Two highly divergent geographically confined mtDNA clades were detected, and these were partly supported by significant differentiation at nuclear DNA level. The clades differ by 9.88% (± 0.40%) mtDNA COI sequence divergence. The southern African clade, which expanded approximately 100 ka, shows no geographical barriers to dispersal and also no IBD. The northern African clade shows signs of IBD, at least five distinct genetic subgroups and an earlier expansion at 200 ka. Conclusion: The phylogeography of the generalist tick is broadly congruent with host vicariance and supports the previously defined African Pleistocene savanna refugia. The magnitude of the sequence divergence between geographically separated genetic lineages suggests that H. truncatum comprises two distinct yet undescribed species. The dispersal of ectoparasites with wide host ranges is dependent on the ability of the various life stages of the parasite to survive in the off-host environment coupled to host movement.