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Population genetics of the endangered Maugean skate (Zearaja maugeana) in Macquarie Harbour, Tasmania

Abstract

The Maugean skate (Zearaja maugeana) has only been recorded in two remote and isolated estuaries on the west coast of Tasmania, Australia. While the population status in one of these estuaries (Bathurst Harbour) is uncertain, it is likely that Macquarie Harbour now represents the sole remaining habitat for this species. Environmental conditions, in particular dissolved oxygen levels and benthic biodiversity, in Macquarie Harbour have deteriorated in recent years, impacted by increased nutrient inputs from an expanding salmonid aquaculture industry. These environmental changes are believed to pose a threat to the persistence of the Maugean skate. In assessing the risks for this rare and range-restricted species, it is vital to consider genetic information when developing management strategies. Both mitochondrial and microsatellite markers showed that the species has low genetic diversity; with no detectable genetic diversity in over 3000 base pairs surveyed from the mitochondrial genome, low average microsatellite heterozygosity (0.35 ± 0.11), a low average number of alleles per locus (2.1 ± 0.4) across eight microsatellite loci and no overall population structure within the microsatellite loci (Fst = − 0.002, p = 0.718 ± 0.012). There was also evidence of a recent bottleneck or founder event, which may explain the low observed genetic diversity. While the species may have existed with low genetic diversity for many generations, the results of this study represent a flag for conservation concern for the Maugean skate. Given that Macquarie Harbour may be its last remaining habitat, any threats to the species resulting in local extinction could equate to global loss of this unique skate species.

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Data availability

Microsatellite genotype data can be found at the University of Queensland library (https://doi.org/10.14264/uql.2018.348) at http://espace.library.uq.edu.au/view/UQ:729708. Mitochondrial sequence data can be found at https://www.ncbi.nlm.nih.gov/genbank/ using the Genbank accession numbers in Table 1.

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Acknowledgements

This study forms part of a doctoral thesis by Kay Weltz and was supported by a Tasmanian Graduate Research Scholarship, the Winifred Violet Scott Charitable Trust, the Holsworth Wildlife Research Endowment and the Fisheries Research and Development Corporation (Project 2013/008). The authors would like to thank Justin Bell, Graeme Ewing, Edward Forbes, David Moreno and Jaime McAllister for field assistance, and Adam Smolenski and Sharee McCammon for assistance and guidance with the laboratory aspects of the study. All research was conducted with approval from the University of Tasmania Animal Ethics Committee (#A0011882) and the Department of Primary Industries, Parks, Water and Environment (Permit #11055).

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Correspondence to Kay Weltz.

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Weltz, K., Lyle, J.M., Semmens, J.M. et al. Population genetics of the endangered Maugean skate (Zearaja maugeana) in Macquarie Harbour, Tasmania. Conserv Genet 19, 1505–1512 (2018). https://doi.org/10.1007/s10592-018-1117-0

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Keywords

  • Endangered elasmobranch
  • Genetic diversity
  • Bottleneck/founder event
  • Extinction risk
  • Conservation
  • Environmental health