Did postglacial sea-level changes initiate the evolutionary divergence of a Tasmanian endemic raptor from its mainland relative?

Christopher Burridge, W Brown, Jessica Wadley, D Nankervis, L Olivier, Michael Gardner, C Hull, R Barbour, Jeremy Austin

    Research output: Contribution to journalArticle

    10 Citations (Scopus)

    Abstract

    Populations on continental islands are often distinguishable from mainland conspecifics with respect to body size, appearance, behaviour or life history, and this is often congruent with genetic patterns. It is commonly assumed that such differences developed following the complete isolation of populations by sea-level rise following the Last Glacial Maximum (LGM). However, population divergence may predate the LGM, or marine dispersal and colonization of islands may have occurred more recently; in both cases, populations may have also diverged despite ongoing gene flow. Here, we test these alternative hypotheses for the divergence between wedge-tailed eagles from mainland Australia (Aquila audax audax) and the threatened Tasmanian subspecies (Aquila audax fleayi), based on variation at 20 microsatellite loci and mtDNA. Coalescent analyses indicate that population divergence appreciably postdates the severance of terrestrial habitat continuity and occurred without any subsequent gene flow. We infer a recent colonization of Tasmania by marine dispersal and cannot discount founder effects as the cause of differences in body size and life history. We call into question the general assumption of post-LGM marine transgression as the initiator of divergence of terrestrial lineages on continental islands and adjacent mainland, and highlight the range of alternative scenarios that should be considered.

    Original languageEnglish
    Article number20132448
    Pages (from-to)20132448
    JournalProceedings of The Royal Society of London Series B: Biological Sciences
    Volume280
    Issue number1773
    DOIs
    Publication statusPublished - 30 Oct 2013

    Keywords

    • Inbreeding depression
    • Last glacial maximum
    • Marine dispersal
    • Sea level
    • Subspecies
    • Vicariance

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