Marked mitochondrial DNA differences between Mediterranean and Atlantic populations of the swordfish, Xiphias gladius

Authors

  • G. KOTOULAS,

    1. *Institute of Marine Biology of Crete, PO Box 2214, 710 03, Iraklion, Crete, Greece
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  • A. MAGOULAS,

    1. *Institute of Marine Biology of Crete, PO Box 2214, 710 03, Iraklion, Crete, Greece
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  • N. TSIMENIDES,

    1. *Institute of Marine Biology of Crete, PO Box 2214, 710 03, Iraklion, Crete, Greece
    2. †Department of Biology, University of Crete, PO Box 1470, 711 10, Iraklion, Crete, Greece
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  • E. ZOUROS

    Corresponding author
    1. *Institute of Marine Biology of Crete, PO Box 2214, 710 03, Iraklion, Crete, Greece
    2. †Department of Biology, University of Crete, PO Box 1470, 711 10, Iraklion, Crete, Greece
    3. ‡Department of Biology and Marine Gene Laboratory, Dalhousie University, Halifax, NS, Canada, B3H4J1
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  • This paper is a product of on-going studies on genetic differentiation, population structure and phylogeography of Mediterranean finfish and shellfish of economic importance in the Institute of Marine Biology of Crete, Greece. Prof. E. Zouros and Dr A. Magoulas are in the staff and Dr G. Kotoulas is a post-doctoral fellow in the Genetics Unit and Prof. N. Tsimenides is in the Fisheries Unit of the Institute.

Fax 902 494 3736. E-mail zouros@ac.da].ca

Abstract

Restriction analysis of mitochondrial DNA (mtDNA) from 204 individuals of swordfish (Xiphias gladius) revealed no differentiation among samples from three sites in the Mediterranean Sea (Greece, Italy, Spain), but a high degree of differentiation between Mediterranean samples and a sample from the Gulf of Guinea. A fifth sample from the Atlantic side of the Straits of Gibraltar (Tarifa) consisted mostly of mitotypes that are common in the Mediterranean, but contained several of mtDNA types of the Guinea sample not found in the Mediterranean. We conclude that, in spite of free migration of swordfish across the Straits of Gibraltar, little genetic exchange occurs between the populations inhabiting the Mediterranean Sea and the tropical Atlantic ocean. This is the first evidence of genetic differentiation among geographic populations of this highly mobile species that supports a world-wide fishery.

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