The influence of host dispersal on the gene flow and genetic diversity of generalist and specialist ectoparasites

Abstract

The dispersal and subsequent gene flow within parasite species is the result of a complex interaction between parasite life history, host life history and abiotic environmental factors. To gain more insights into the drivers responsible for parasite dispersal, COI mtDNA genetic data derived from six southern African generalist parasite species, including fleas, mites and ticks were compared with four specialist species from the same  geographic region. Generalist tick species represented by Amblyomma hebraeum, Hyalomma truncatum and H. rufipes all occur temporarily on highly mobile ungulate hosts and showed high levels of haplotypic genetic diversity and high levels of dispersal with an average intraspecific global Fst (population differentiation index) value of 0.27 (±0.13). Generalist parasites, such as fleas, Listropsylla agrippinae and Chiastopsylla rossi, and  one mite species, Laelaps muricola, that are all semi-permanent on the host and restricted to less mobile hosts species, showed a similar high level of genetic diversity, but an intermediate average Fst value of 0.67 (±0.11). Highly specialised semi-permanent parasites, such as the mite L. giganteus and the permanent lice Polyplax praomydis, Hoplopleura patersoni and P. arvicanthis recorded the lowest level of genetic diversity and a low level of gene flow among geographic sampling localities with an average Fst value of 0.95 (±0.05). This study provides strong support for the  Specialist Generalist Variation Hypothesis (SGVH) and highlights the role that host dispersal and host specialisation by parasites play in the dispersal and evolution of ectoparasites.

Keywords: isolation by distance, mtDNA COI, population structure, southern Africa, Specialist Generalist Variation  Hypothesis