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Evidence for ecological speciation in the sister species Candidula unifasciata (Poiret, 1801) and C. rugosiuscula (Michaud, 1831) (Helicellinae, Gastropoda)

Authors

  • MARKUS PFENNINGER,

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    1. Abteilung Ökologie und Evolution, Zoologisches Institut der J.W.Goethe-Universität, Bio-Campus Siesmayerstraße, D-60054 Frankfurt/Main
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  • ANNEKATRIN EPPENSTEIN,

    1. Abteilung Ökologie und Evolution, Zoologisches Institut der J.W.Goethe-Universität, Bio-Campus Siesmayerstraße, D-60054 Frankfurt/Main
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  • FRÉDÉRIC MAGNIN

    1. IMEP UMR 6116 Case 461, Faculté des Sciences et Techniques de St. Jerome, 13997 Marseille Cedex 20, France
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Corresponding   author.   E-mail: Pfenninger@zoology.uni-frankfurt.de

Abstract

This paper studies the speciation of two land snail species in south-east France. By using two mitochondrial and one nuclear gene, the species are shown to be sister species within the larger clade of western European Candidula species. The species never occurred syntopically, but a narrow contact zone population was identified. Recent range expansions inferred from phylogeographical methods indicated that the present day distributions are not limited by the colonization capacity of the species. Analysis of environmental variables suggested distribution along an ecotone. The gastropod community is also correlated to this gradient. Morphometric shell analysis showed that the divergence between the sister species is a result of desiccation-resistant shell characters. We therefore conclude that the cause for the ecological speciation is most probably the establishment of the Mediterranean climate ≈ 3.2 mya. A model of ecological speciation with a moving ecotone is put forward. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 79, 611–628.

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