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Faunal changes and geographic crypticism indicate the occurrence of a biogeographic transition zone along the southern East Pacific Rise

Authors

  • M. Matabos,

    Corresponding author
    1. Muséum National d’Histoire Naturelle, Département Milieux et Peuplements Aquatiques, UMR BOREA 7208 (MNHN, UPMC, CNRS), CP 53, 61 rue Buffon, F-75231 Paris Cedex 05, France
    2. CNRS, UMR 7144, F-29682 Roscoff Cedex, France
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  • S. Plouviez,

    1. CNRS, UMR 7144, F-29682 Roscoff Cedex, France
    2. Université Pierre et Marie Curie, Station Biologique de Roscoff, UMR 7144, Laboratoire Adaptation et Diversité en Milieu Marin, F-29680 Roscoff Cedex, France
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  • S. Hourdez,

    1. CNRS, UMR 7144, F-29682 Roscoff Cedex, France
    2. Université Pierre et Marie Curie, Station Biologique de Roscoff, UMR 7144, Laboratoire Adaptation et Diversité en Milieu Marin, F-29680 Roscoff Cedex, France
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  • D. Desbruyères,

    1. Ifremer, Département Etude des Ecosystèmes Profonds, BP70, F-29280 Plouzané, France
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  • P. Legendre,

    1. Département de Sciences Biologiques, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC, H3C 3J7, Canada
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  • A. Warén,

    1. Swedish Museum of Natural History, Box 5007, SE-10405, Stockholm, Sweden
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  • D. Jollivet,

    1. CNRS, UMR 7144, F-29682 Roscoff Cedex, France
    2. Université Pierre et Marie Curie, Station Biologique de Roscoff, UMR 7144, Laboratoire Adaptation et Diversité en Milieu Marin, F-29680 Roscoff Cedex, France
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  • E. Thiébaut

    1. CNRS, UMR 7144, F-29682 Roscoff Cedex, France
    2. Université Pierre et Marie Curie, Station Biologique de Roscoff, UMR 7144, Laboratoire Adaptation et Diversité en Milieu Marin, F-29680 Roscoff Cedex, France
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M. Matabos, School of Earth and Ocean Sciences, University of Victoria, PO Box 3065, STN CSC, British Columbia, Vic., V8W 3V6, Canada.
E-mail: mmatabos@uvic.ca

Abstract

Aim  Deep-sea hydrothermal vents have now been reported along all active mid-ocean ridges and back-arc basins, but the boundaries of biogeographic entities remain questionable owing to methodological issues. Here we examine biogeographic patterns of the vent fauna along the East Pacific Rise (EPR) and determine the relative roles of regional and local factors on the distribution of biodiversity associated with mussel beds along a poorly explored zone, the southern EPR (SEPR).

Location  East Pacific Rise.

Methods  A species list of macrobenthic invertebrates along the EPR was compiled from the literature and supplemented with data recovered during the French research cruise BIOSPEEDO carried out in 2004 along the SEPR. Biogeographic patterns were assessed by combining the identification of morphological species with a molecular barcoding approach. A multivariate regression tree (MRT) analysis was performed to identify any geographic breaks, and an empirical distribution of species richness was compared with predictions provided by a mid-domain effect model. Macrofaunal community structure associated with mussel beds along the SEPR was analysed in relation to environmental factors using cluster and canonical redundancy analyses.

Results  Sequencing of the cytochrome c oxidase subunit I gene revealed the occurrence of several cryptic species complexes along the EPR, with the equator separating the southern and northern clades. Furthermore, during the BIOSPEEDO cruise at least 10 still unnamed species were collected between 7°25′ S and 21°33′ S. The shift in community structure identified by MRT analysis was located south of 17°34′ S or south of 13°59′ S, depending on the data used, suggesting that the southern part of the SEPR (17°25′–21°33′ S) constitutes a biogeographic transition zone in the vent fauna along the EPR. At a regional scale, latitude combined with the type of venting was significantly correlated with the community structure associated with mussel beds.

Main conclusions  Together, the molecular data, in situ observations, and the distribution of species suggest that the high diversity of vent fauna species presently observed between 17°25′ S and 21°33′ S is probably a result of the overlap of several distinct biogeographic provinces. We argue that this area thus constitutes a biogeographic vent fauna transition zone along the EPR.

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