25 Jun 2018 - 15:45

The Plant Conservation Unit (PCU) is pleased to announce the publication of an exciting new paper by Heidi Hirsch, David M. Richardson, Fiona A. C. ImpsonCatharina Kleinjan (PCU) and Johannes J. Le Roux in the journal of Tree Genetics & Genomes. The article is titled, "Historical range contraction, and not taxonomy, explains the contemporary genetic structure of the Australian tree Acacia dealbata Link” and was published online in June 2018. The abstract is provided below but the full paper may be downloaded here.

"Irrespective of its causes, strong population genetic structure indicates a lack of gene flow. Understanding the processes that underlie such structure, and the spatial patterns it causes, is valuable for conservation efforts such as restoration. On the other hand, when a species is invasive outside its native range, such information can aid management in the non-native range. Here we explored the genetic characteristics of the Australian tree Acacia dealbata in its native range. Two subspecies of A. dealbata have previously been described based on morphology and environmental requirements, but recent phylogeographic data raised questions regarding the validity of this taxonomic subdivision. The species has been widely planted within and outside its native Australian range and is also a highly successful invasive species in many parts of the world. We employed microsatellite markers to investigate the population genetic diversity and structure among 42 A. dealbata populations from across the species’ native range (see Fig below). We also tested whether environmental variables purportedly relevant for the putative separation of subspecies are linked with population genetic differentiation. We found no relationship between population genetic structure of A. dealbata in Australia and these environmental features. Rather, we identified two geographically distinct genetic clusters that corresponded with populations in the northeastern part of mainland Australia, and the southern mainland and Tasmanian range of the species. Our results do not support the taxonomic subdivision of the species into two distinct subspecies based on environmental features. We therefore assume that the observed morphological differences between the putative subspecies are plastic phenotypic responses. This study provides population genetic information that will be useful for the conservation of the species within Australia as well as to better understand the invasion dynamics of A. dealbata."

Fig. Native populations of Acacia dealbata in Australia sampled for this study (triangles) and the occurrence records of the two putative A. dealbata subspecies which were used for the niche modeling approach by Hirsch et al. (2017). The information is shown in two maps for the sake of clarity due to the strong overlap between occurrence records for the putative subspecies. a Sampled populations and A. dealbata ssp. dealbata occurrence records (yellow squares). b Sampled populations and A. dealbata ssp. subalpina occurrence records (blue squares). In both maps, the sample locations are differentiated according to their altitude (i.e., red triangles = location below 1000 m a.s.l.; dark blue triangles = locations above 1000 m a.s.l.)