Managing the risk of genetic swamping of a rare and restricted tree
Hybridisation is a complex process that has important evolutionary consequences. In the case of rare species, a comprehensive understanding of inter-specific hybridisation can be critical for their conservation and management. Eucalyptus tetrapleura is a rare species of ironbark that is restricted to a 40 km × 100 km area around Grafton on the North Coast of New South Wales (Australia), and is distinctive in that it has four ribs on the sides of its buds and fruits. In recent years, central populations of E. tetrapleura have been cleared to facilitate upgrades to one of the major highways in eastern Australia. This has led to increased habitat fragmentation, and there are now concerns that the species is at risk of genetic swamping by more common ironbark relatives. In this study, we investigated the population genetics and patterns of gene flow in E. tetrapleura. We used DArTseq to genotype samples collected from across the known distribution of E. tetrapleura, as well as leaf material collected from co-occurring ironbark species. We found that while E. tetrapleura was a distinct evolutionary lineage, there was evidence of gene flow between this species and other ironbarks. Furthermore, many populations that had been identified as E. tetrapleura on the basis of morphology were of hybrid origin, thus the range of the species was much smaller than previously thought. Overall, our findings demonstrate how genomic methods can improve our understanding of admixture across closely related lineages, which can be used to inform the restoration of rare species.
KeywordsConservation Diversity Arrays Technology (DArTseq) Eucalypts Hybridisation
We thank John O’Donnell from the Roads and Maritime Service New South Wales for assistance in the field. We thank staff from the Royal Botanic Garden Sydney, especially Peter D. Wilson, Jason Bragg and Hannah McPherson for assistance with the data analysis. This research was made possible by a contract (with financial support) from the Roads and Maritime Service New South Wales. All collection of samples and vouchers in National Parks for this study operated under a scientific licence (SL101766). We thank two anonymous reviewers for comments that enabled us to improve the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Genotype data is available from the Dryad Digital Repository. https://doi.org/10.5061/dryad.76t6j77.
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