Persistence of Anopheles arabiensis during the severe dry season conditions in Senegal: an indirect approach using microsatellite loci

Authors

  • Frédéric Simard,

    Corresponding author
    1. Laboratoire de Zoologie Médicale, French Institut de Recherche pour le Développement (IRD), Institut Pasteur, Dakar, Sénégal,
    2. Division of Parasitic Diseases, Centers for Disease Control and Prevention, Chamblee, GA, USA,
      Frédéric Simard, Division of Parasitic Diseases, Centers for Diseases Control and Prevention, MS F-22, 4770 Buford Highway, Chamblee, GA 30341, USA. Tel.: (770) 488 4634; fax: (770) 488 4258; e-mail: fes3@cdc.gov
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  • Tovi Lehmann,

    1. Division of Parasitic Diseases, Centers for Disease Control and Prevention, Chamblee, GA, USA,
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  • Jean-Jacques Lemasson,,

    1. Laboratoire de Zoologie Médicale, French Institut de Recherche pour le Développement (IRD), Institut Pasteur, Dakar, Sénégal,
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  • Mathurin Diatta,

    1. Laboratoire de Zoologie Médicale, French Institut de Recherche pour le Développement (IRD), Institut Pasteur, Dakar, Sénégal,
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  • Didier Fontenille

    1. Laboratoire de l’Institut de Recherche pour le Développement (IRD), Organisation de lutte Contre les grandes Endémies en Afrique Centrale (OCEAC), Yaoundé, Cameroun
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Frédéric Simard, Division of Parasitic Diseases, Centers for Diseases Control and Prevention, MS F-22, 4770 Buford Highway, Chamblee, GA 30341, USA. Tel.: (770) 488 4634; fax: (770) 488 4258; e-mail: fes3@cdc.gov

Abstract

Variation at nine microsatellite loci was investigated to understand how Anopheles arabiensis populations survive the dry season in the sahelian region of Senegal. Low estimates of genetic differentiation (FST = 0.012, RST = 0.009) between two populations, 250 km apart, suggested extensive gene flow across this distance. Despite extreme seasonal fluctuation in abundance with dry season minima in which mosquitoes virtually disappeared, allele frequencies remained stable over time in the village of Barkedji from August 1994 to December 1997 (including four rainy seasons and three dry seasons). The effective population size (Ne) was estimated to be 601 with 95% CI (281, 1592), providing strong evidence against annual bottlenecks. Differences in measures of genetic diversity and linkage disequilibrium between the dry and the rainy seasons were not detected. These results suggest that despite extreme minima in local density, An. arabiensis maintains large permanent deme spread out over large area.

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