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Did postglacial sea-level changes initiate the evolutionary divergence of a Tasmanian endemic raptor from its mainland relative?
journal contributionposted on 2023-05-17, 21:07 authored by Christopher BurridgeChristopher Burridge, Brown, WE, Wadley, J, Nankervis, DL, Olivier, L, Gardner, MG, Hull, C, Barbour, R, Austin, JJ
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.
Publication titleProceedings of the Royal Society of London: B
Department/SchoolSchool of Natural Sciences
PublisherRoyal Soc London
Place of publication6 Carlton House Terrace, London, England, Sw1Y 5Ag
Rights statementCopyright 2013 The Royal Society