Phylogeography of a mite, Halozetes fulvus, reflects the landscape history of a young volcanic island in the sub-Antarctic

Authors

  • ELIZABETH MORTIMER,

    1. Department of Botany and Zoology, Evolutionary Genomics Group, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
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    • Present address: Subunit Vaccine Group, Department of Molecular and Cell Biology, University of Cape Town, Rondebosch 7701, South Africa.

  • BETTINE JANSEN VAN VUUREN,

    Corresponding author
    1. Department of Botany and Zoology, Evolutionary Genomics Group, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
    2. Department of Botany and Zoology, Centre for Invasion Biology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
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  • K. IAN MEIKLEJOHN,

    1. Department of Geography, Rhodes University, PO Box 94, Grahamstown, 6140, South Africa
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  • STEVEN L. CHOWN

    1. Department of Botany and Zoology, Centre for Invasion Biology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
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E-mail: bjvv@sun.ac.za

Abstract

Previous studies of the microarthropods of Marion Island, Southern Ocean, documented high mitochondrial COI (cytochrome c oxidase subunit I) haplotype diversity and significant genetic structure, which were ascribed to landscape subdivision. In this paper we revisit these ideas in light of new geomorphological evidence indicating a major lineament orientated along N26.5°E. Using the microarthropod Halozetes fulvus, we test the hypothesis that the eastern and western sides of the island show different population genetic patterns, corresponding to the previously unrecognized geological separation of these regions, and perhaps also with differences in climates across the island and further landscape complexity. Mitochondrial COI data were collected for 291 H. fulvus individuals from 30 localities across the island. Notwithstanding our sampling effort, haplotype diversity was under-sampled as indicated by rarefaction analyses. Overall, significant genetic structure was found across the island as indicated by ΦST analyses. Nested clade phylogeographical analyses suggested that restricted gene flow (with isolation-by-distance) played a role in shaping current genetic patterns, as confirmed by Mantel tests. At the local scale, coalescent modelling revealed two different genetic patterns. The first, characterizing populations on the south-western corner of the island, was that of low effective population size and high gene flow. The converse was found on the eastern side of Marion Island. Taken together, substantial differences in spatial genetic structure characterize H. fulvus populations across Marion Island, in keeping with the hypothesis that the complex history of the island, including the N26.5°E geological lineament, has influenced population genetic structure. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 131–145.

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