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Marine Ecology Progress Series

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MEPS 455:229-244 (2012)  -  DOI:

Population genetics of Australian white sharks reveals fine-scale spatial structure, transoceanic dispersal events and low effective population sizes

Dean C. Blower1,*, John M. Pandolfi1,2, Barry D. Bruce3, Maria del C. Gomez-Cabrera1,2, Jennifer R. Ovenden4

1School of Biological Sciences, and 2Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, St Lucia, Queensland 4072, Australia
3Wealth from Oceans Flagship, Commonwealth Scientific and Industrial Research Organization (CSIRO) Marine and Atmospheric Research, Hobart, Tasmania 7000, Australia
4Molecular Fisheries Laboratory, Queensland Government Department of Employment, Economic Development and Innovation, St Lucia, Queensland 4072, Australia

ABSTRACT: Despite international protection of white sharks Carcharodon carcharias, important conservation parameters such as abundance, population structure and genetic diversity are largely unknown. The tissue of 97 predominately juvenile white sharks sampled from spatially distant eastern and southwestern Australian coastlines was sequenced for the mitochondrial DNA (mtDNA) control region and genotyped with 6 nuclear-encoded microsatellite loci. MtDNA population structure was found between the eastern and southwestern coasts (FST = 0.142, p < 0.0001), implying female reproductive philopatry. This concurs with recent satellite and acoustic tracking findings which suggest the sustained presence of discrete east coast nursery areas. Furthermore, population subdivision was found between the same regions with biparentally inherited microsatellite markers (FST = 0.009, p < 0.05), suggesting that males may also exhibit some degree of reproductive philopatry; 5 sharks captured along the east coast had mtDNA haplotypes that resembled western Indian Ocean sharks more closely than Australian/New Zealand sharks, suggesting that transoceanic dispersal, or migration resulting in breeding, may occur sporadically. Our most robust estimate of contemporary genetic effective population size was low and close to thresholds at which adaptive potential may be lost. For a variety of reasons, these contemporary estimates were at least 1, possibly 2, orders of magnitude below our historical effective size estimates. Population decline could expose these genetically isolated populations to detrimental genetic effects. Regional Australian white shark conservation management units should be implemented until genetic population structure, size and diversity can be investigated in more detail.

KEY WORDS: Carcharodon carcharias · Population structure · Philopatry · Effective population size · Population genetics · Conservation · Nursery areas · Reproductive strategy

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Cite this article as: Blower DC, Pandolfi JM, Bruce BD, Gomez-Cabrera MdC, Ovenden JR (2012) Population genetics of Australian white sharks reveals fine-scale spatial structure, transoceanic dispersal events and low effective population sizes. Mar Ecol Prog Ser 455:229-244.

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