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This study investigates the genetic structure and phylogeography of a broadcast spawning bivalve mollusc, Pinctada maxima, throughout the Indo- West Pacific and northern Australia. DNA sequence variation of the mitochondrial cytochrome oxidase subunit I ( COI) gene was analysed in 367 individuals sampled from nine populations across the Indo- West Pacific. Hierarchical AMOVA indicated strong genetic structuring amongst populations (ΦST = 0.372, P < 0.001); however, sequence divergence between the 47 haplotypes detected was low (maximum 1.8% difference) and no deep phylogenetic divergence was observed. Results suggest the presence of genetic barriers isolating populations of the South China Sea and central Indonesian regions, which, in turn, show patterns of historical separation from northern Australian regions. In P. maxima, historical vicariance during Pleistocene low sea levels is likely to have restricted planktonic larval transport, causing genetic differentiation amongst populations. However, low genetic differentiation is observed where strong ocean currents are present and is most likely due to contemporary larval transport along these pathways. Geographical association with haplotype distributions may indicate signs of early lineage sorting arising from historical population separations, yet an absence of divergent phylogenetic clades related to geography could be the consequence of periodic pulses of high genetic exchange. We compare our results with previous microsatellite DNA analysis of these P. maxima populations, and discuss implications for future conservation management of this species. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ••, ••-••. [ABSTRACT FROM AUTHOR]

Sea urchins of the genus Tripneustes are among the most abundant and ecologically important pan-tropical marine invertebrates. Recognized as potent ecosystem engineers due to their intense grazing of macroalgae and sea grass and highly valued for their gonads, wild populations of Tripneustes are commercially exploited for fisheries and aquaculture. Recently, a new species, Tripneustes kermadecensis (Bronstein et al. 2017), was described from the southern Pacific Ocean, off the Kermadec Islands, near the tropical/sub-tropical transition zone. Here, we explore the range of Tripneustes and, in particular, T. kermadecensis by morphological and genetic tools to determine whether it also occurs in Australia. We report, for the first time, the presence of a second Tripneustes species, T. kermadecensis, from Australia. We show that T. kermadecensis is in fact highly abundant throughout most of sub-tropical eastern Australia, where it occurs in association with coral and temperate reefs and has been recognized for decades as the 'lamington sea urchin'. As commercial exploitation and stock-release programs of Tripneustes are rapidly expanding, and as global warming causes tropicalization of eastern Australia, driving the southern expansion of its congener T. gratilla, we call for re-evaluation of the conservation vulnerability of T. kermadecensis along the Australian continent and action by the aquaculture industry to genetically confirm the species identity of stocks in their facilities. [ABSTRACT FROM AUTHOR]