Population genetics, demographics and implications for conservation of Brachychiton sp. Ormeau, a Critically Endangered rainforest tree

Abstract

Brachychiton sp. Ormeau (L.H. Bird AQ435851), commonly known as the Ormeau bottle tree, is listed as Critically Endangered under the Environment Protection and Biodiversity Conservation Act 1999. Undescribed and extremely rare, it is known only from several sites within a very small geographic range near Ormeau in south-east Queensland. Using microsatellite markers developed for this study, we found Brachychiton sp. Ormeau to be genetically distinct from several closely related species, confirming unique specific status. We also assessed levels of genetic variation found within B. sp. Ormeau subpopulations to provide recommendations for recovery projects. The species exhibited low levels of variation (He = 0.065); however, no evidence of inbreeding (F = –0.290). We infer that the species’ current restricted range and low genetic diversity is due to a combination of the effects of well documented climate shifts across the Plio-Pleistocene, exacerbated by extensive rates of relatively recent and ongoing human-mediated habitat loss. Our results suggest that, to enhance the long-term viability of B. sp. Ormeau, the most effective recovery strategies include the protection and restoration of the existing remnant habitat, as well as enhancement of local subpopulations and existing isolated plants, with additional plants to increase the genetic diversity.