Oral Presentation Australian Freshwater Sciences Society Conference 2018

Gene flow, dispersal and genetic structure in river cooba, a true riverine specialist (#15)

Bruce Murray 1 , Michael Reid 1 , Samantha Capon 2 , Shu-Biao Wu 3
  1. Geography and Planning, University of New England, Armidale, New South Wales, Australia
  2. Australian Rivers Institute, Griffith University , Nathan, Queensland, Australia
  3. School of Environmental and Rural Science , University of New England, Armidale, New South Wales, Australia

This research explores patterns of gene flow, dispersal and spatial genetic structure in populations of Acacia stenophylla and the effects, if any, of the river network on these patterns.

Phyllode tissue samples were collected from 127 individual A. stenophylla plants located on 7 different rivers of the northern Murray Darling Basin (MDB). Individuals were genotyped at 13 novel microsatellite loci. Spatial and genetic data were analysed to detect relationships between landscape characteristics and population differentiation, patterns of gene flow and spatial genetic structure, and possible modes of dispersal.

Weak spatial genetic structure and low levels of pairwise genetic differentiation between sub-populations suggest high levels of gene flow between sub-populations of A. stenophylla in the northern MDB. Differences between sub-populations within river systems, sub-populations among river systems and sub-populations overall were all highly significant; however, differences between sub-populations among river systems (FST = 0.028) were considerably larger than differences between sub-populations within river systems (FST = 0.016). STRUCTURE analysis identified two genetic clusters. Sub-populations from the Lower Balonne and Darling River systems were dominated by cluster 1.  Individuals from the Paroo and Warrego River populations showed mixed ancestry with individuals descending from clusters 1 and 2. Significant relationships were found between pairwise distances along the river and pairwise genetic differentiation. No significant relationship was found between straight-line distance and pairwise genetic differentiation. Finally, two variables (river distance and proportion of no flow) predicted 68% of the variation in pairwise genetic distance between sub-populations.

Results are discussed in terms of what they mean for gene flow and dispersal of A. stenophylla in the northern MDB. In addition, comparisons are made between this study and previously published results for river red gum. Management implications will be explored.