Recent evolution of host-associated divergence in the seabird tick Ixodes uriae

Authors

  • FLORENT KEMPF,

    1. Génétique et Evolution des Maladies Infectieuses), UMR CNRS-IRD 2724, IRD, 911 avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France
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  • THIERRY BOULINIER,

    1. Centre d’Ecologie Fonctionnelle et Evolutive, CNRS UMR 5175, 1919 Route de Mende 34293 Montpellier, France
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  • THIERRY DE MEEÛS,

    1. Laboratoire de recherches et de coordination sur les Trypanosomoses, UMR177 IRD/CIRAD, TA A-17/G, Campus International de Baillarguet, 34398 Montpellier Cedex 5, France
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  • CÉLINE ARNATHAU,

    1. Génétique et Evolution des Maladies Infectieuses), UMR CNRS-IRD 2724, IRD, 911 avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France
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  • KAREN D. McCOY

    1. Génétique et Evolution des Maladies Infectieuses), UMR CNRS-IRD 2724, IRD, 911 avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France
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  • This work was part of F. Kempf’s dissertation on the evolution of host specialization in two vectors of Lyme disease bacteria, Ixodes uriae and Ixodes ricinus. T. De Meeûs’ major interests focus on theoretical and empirical population genetic studies in parasitic systems. C. Arnathau works on the population genetics of vectors and associated microparasites. The results presented in this study are part of a long-term study conducted by K.D. McCoy and T. Boulinier on the evolutionary ecology of the interaction among seabirds, I. uriae and Lyme disease bacteria.

Florent Kempf, Fax: (33) 4 67 41 62 99; E-mail: florent.kempf@mpl.ird.fr

Abstract

Ecological interactions are an important source of rapid evolutionary change and thus may generate a significant portion of novel biodiversity. Such changes may be particularly prevalent in parasites, where hosts can induce strong selection for adaptation. To understand the relative frequency at which host-associated divergences occur, it is essential to examine the evolutionary history of the divergence process, particularly when it is occurring over large geographical scales where both geographical and host-associated isolation may playa part. In this study, we use population genetics and phylogeography to study the evolutionary history of host-associated divergence in the seabird tick Ixodes uriae (Acari, Ixodidae). We compare results from microsatellite markers that reflect more ecological timescales with a conserved mitochondrial gene (COIII) that reflects more ancient divergence events. Population structure based on microsatellites showed clear evidence of host-associated divergence in all colonies examined. However, isolated populations of the same host type did not always group together in overall analyses and the genetic differentiation among sympatric host races was highly variable. In contrast, little host or geographical structure was found for the mitochondrial gene fragment. These results suggest that host race formation in I. uriae is a recent phenomenon, that it may have occurred several times and that local interactions are at different points in the divergence process. Rapid divergence in I. uriae implies a strong interaction with its local host species, an interaction that will alter the ecological dynamics of the system and modify the epidemiological landscape of circulating micropathogens.

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