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Founder effects, inbreeding and effective sizes in the Southern cattle tick: the effect of transmission dynamics and implications for pest management

Authors

  • BROU BASILE KOFFI,

    1. Génétique et Evolution des Maladies Infectieuses (G.E.M.I.), UMR CNRS-IRD 2724, Centre IRD, 911 avenue Agropolis, BP 64501, 34 394 Montpellier Cedex 5, France,
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  • THIERRY DE MEEÛS,

    1. Génétique et Evolution des Maladies Infectieuses (G.E.M.I.), UMR CNRS-IRD 2724, Centre IRD, 911 avenue Agropolis, BP 64501, 34 394 Montpellier Cedex 5, France,
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  • NICOLAS BARRÉ,

    1. IAC/CIRAD UR 22, BP 73, 98890 Païta, Nouvelle Calédonie, France
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  • PATRICK DURAND,

    1. Génétique et Evolution des Maladies Infectieuses (G.E.M.I.), UMR CNRS-IRD 2724, Centre IRD, 911 avenue Agropolis, BP 64501, 34 394 Montpellier Cedex 5, France,
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  • CÉLINE ARNATHAU,

    1. Génétique et Evolution des Maladies Infectieuses (G.E.M.I.), UMR CNRS-IRD 2724, Centre IRD, 911 avenue Agropolis, BP 64501, 34 394 Montpellier Cedex 5, France,
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  • CHRISTINE CHEVILLON

    1. Génétique et Evolution des Maladies Infectieuses (G.E.M.I.), UMR CNRS-IRD 2724, Centre IRD, 911 avenue Agropolis, BP 64501, 34 394 Montpellier Cedex 5, France,
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Christine Chevillon, Fax +33 (0)467 41 62 99; E-mail: christine.chevillon@mpl.ird.fr

Abstract

Since its immigration in the Pacific island of New Caledonia in 1942 (i.e. about 240 tick-generations ago), the cattle tick Boophilus microplus has experienced a remarkable adaptive diversification there. In order to better understand the population factors involved, we have investigated the B. microplus population structure on that main host-species, Bos taurus. This study was based microsatellite loci and confirmed that the island colonization came along with a significant bottleneck. Knowledge on B. microplus biology led us to expect B. microplus populations to be composed of highly inbred lineages irregularly dispatched among the individual hosts belonging to the same herds. Instead, this study evidenced a weak inbreeding level and an absence of genetic differentiation within herds. Complementarily, a significant signal of isolation by distance exhibited that human-traffic of cattle does not promote high tick dispersal within the island. Finally, the tick density was found to be about a few hundreds of reproducing adults per squared kilometre, for a gene dispersal range of about a few hundred metres per tick generation. Results are discussed with regard to the evolution of new adaptive changes.

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