Original Article | Published:

Identifying environmental correlates of intraspecific genetic variation

Heredity volume 117, pages 155164 (2016) | Download Citation

Abstract

Genetic variation is critical to the persistence of populations and their capacity to adapt to environmental change. The distribution of genetic variation across a species’ range can reveal critical information that is not necessarily represented in species occurrence or abundance patterns. We identified environmental factors associated with the amount of intraspecific, individual-based genetic variation across the range of a widespread freshwater fish species, the Murray cod Maccullochella peelii. We used two different approaches to statistically quantify the relative importance of predictor variables, allowing for nonlinear relationships: a random forest model and a Bayesian approach. The latter also accounted for population history. Both approaches identified associations between homozygosity by locus and both disturbance to the natural flow regime and mean annual flow. Homozygosity by locus was negatively associated with disturbance to the natural flow regime, suggesting that river reaches with more disturbed flow regimes may support larger, more genetically diverse populations. Our findings are consistent with the hypothesis that artificially induced perennial flows in regulated channels may provide greater and more consistent habitat and reduce the frequency of population bottlenecks that can occur frequently under the highly variable and unpredictable natural flow regime of the system. Although extensive river regulation across eastern Australia has not had an overall positive effect on Murray cod numbers over the past century, regulation may not represent the primary threat to Murray cod survival. Instead, pressures other than flow regulation may be more critical to the persistence of Murray cod (for example, reduced frequency of large floods, overfishing and chemical pollution).

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Acknowledgements

This work was supported by ARC Grant LP110200017 to Monash University, Flinders University of South Australia and the University of Canberra, with Partner Organization University of Montana. Funding and other support was contributed by industry Partner Organizations ACTEW Corporation, Department of Sustainability and Environment (Victoria) (now within Department of Environment, Land, Water & Planning), Fisheries Victoria (now within Department of Economic Development, Jobs, Transport and Resources), Melbourne Water and Fisheries New South Wales. KAH was supported by the Holsworth Wildlife Research Endowment and an Australian Postgraduate Award through Monash University. We thank Jim Thomson for statistical support and the associate editor and three anonymous reviewers for comments on earlier drafts.

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Affiliations

  1. School of Biological Sciences, Monash University, Clayton, Victoria, Australia

    • K A Harrisson
    • , A Pavlova
    •  & P Sunnucks
  2. School of Physics & Astronomy, Monash University, Clayton, Victoria, Australia

    • J D L Yen
  3. Department of Primary Industries, DPI Fisheries, Narrandera, New South Wales, Australia

    • M L Rourke
  4. Department of Primary Industries, DPI Fisheries, Batemans Bay Fisheries Office, Batemans Bay, New South Wales, Australia

    • D Gilligan
  5. Fisheries Victoria, Department of Economic Development, Jobs, Transport and Resources, Alexandra, Victoria, Australia

    • B A Ingram
  6. Arthur Rylah Institute, Department of Environment, Land, Water & Planning, Heidelberg, Victoria, Australia

    • J Lyon
    •  & Z Tonkin

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The authors declare no conflict of interest.

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Correspondence to K A Harrisson.

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DOI

https://doi.org/10.1038/hdy.2016.37

Supplementary Information accompanies this paper on Heredity website (http://www.nature.com/hdy)

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