Recent studies show that host switching is much more frequent than originally believed and constitutes an important driver in evolution of host-parasite associations. However, its frequency and ecological mechanisms at the population level have been rarely investigated. We address this issue by analyzing phylogeny and population genetics of an extensive sample, from a broad geographic area, for commonly occurring parasites of the genus Eimeria within the abundant rodent genera Apodemus, Microtus and Myodes, using two molecular markers. At the most basal level, we demonstrate polyphyletic arrangement, i.e. multiple origin, of the rodent-specific clusters within the Eimeria phylogeny, and strong genetic/phylogenetic structure within these lineages determined at least partially by specificities to different host groups. However, a novel and the most important observation is a repeated occurrence of host switches among closely related genetic lineages which may become rapidly fixed. Within the studied model, this phenomenon applies particularly to the switches between the eimerians from Apodemus flavicollis/Apodemus sylvaticus and Apodemus agrarius groups. We show that genetic differentiation and isolation between A. flavicollis/A. sylvaticus and A. agrarius faunas is a secondary recent event and does not reflect host-parasite coevolutionary history. Rather, it provides an example of rapid ecology-based differentiation in the parasite population.

Department of Parasitology Faculty of Science University of South Bohemia Branišovská 1760 370 05 České Budějovice Czech Republic

Department of Parasitology Faculty of Science University of South Bohemia Branišovská 1760 370 05 České Budějovice Czech Republic; Biology Centre Institute of Parasitology Academy of Sciences of the Czech Republic Branišovská 31 370 05 České Budějovice Czech Republic

Institute of Parasitology and Institute of Zoology Slovak Academy of Sciences Hlinkova 3 040 01 Košice Slovakia

References provided by Crossref.org

Phylogeography of the parasitic mite Laelaps agilis in Western Palearctic shows lineages lacking host specificity but possessing different demographic histories

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Generalist Eimeria species in rodents: Multilocus analyses indicate inadequate resolution of established markers

Detection and quantification of house mouse Eimeria at the species level - Challenges and solutions for the assessment of coccidia in wildlife