Disentangling the evolutionary history of three related shrub species using genome-wide molecular markers
Understanding population genetic structure provides insight into historic population connectivity, and is largely driven by migration, population size, and species life history. During the last glacial maximum, sea levels around the biogeographically interesting, but poorly studied, South Australian coastal plains and geosyncline were thought to be sufficiently low that three prominent peninsulas (Fleurieu, Yorke, Eyre) and a large offshore island (Kangaroo Island) formed a continuous landmass. However, the degree to which population genetic structure in this region has been shaped by biogeography remains largely untested. Here, we use genome-wide SNP data from three Goodenia shrub species with contrasting growth forms to assess how historical and contemporary processes have shaped population genetic structure. These species occur commonly throughout South Australia and are used extensively in revegetation. The two woody species (Goodenia varia, G. ovata) displayed low genetic differentiation across the southern parts of the peninsulas and island, reflecting historical landscape connectivity. The third more-herbaceous species (G. amplexans) displayed higher genetic structure across the land features, reflecting contemporary disconnectivity. Kangaroo Island and the southern Flinders Ranges had relatively high genetic diversity, providing further evidence that they were important putative Pleistocene refugia. We demonstrate that historic changes in landscape and possible migration to and from refugia, have shaped the population genetic structure in these closely related shrubs, which may have been influenced by contemporary factors and small population sizes. We highlight the importance of using multi-species designs when studying historical population connectivity in understudied regions of the world.
KeywordsGenetic resource management Genotyping-by-sequencing Goodenia Life history traits Population genetic structure Shrubs
The authors wish to thank Bianca Dunker, Connie Rowe, Duncan Jardine, Ed Biffin, John McDonald, Kimberly McCallum and everyone else who assisted with sample collection. Thank you to DWENR and park staff for their assistance with fieldwork. The authors also thank the Australian Research Council for funding support (DE150100542 awarded to MFB; DP150103414 awarded to AJL and MFB).
MFB, DK, AJL designed the experiments. DK, MC, MFB analysed the data. DK wrote the first draft of the manuscript. All authors contributed substantially to revisions.
Conflict of interest
The authors declare no conflicts of interest.
Reads and mapping files have been archived at the NCBI SRA (Accession Number PRJNA543186).
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