Population genetic analysis of a medicinally significant Australian rainforest tree, Fontainea picrosperma C.T. White (Euphorbiaceae): biogeographic patterns and implications for species domestication and plantation establishment.

R W Lamont,G C Conroy,S M Ogbourne,P Reddell

doi:10.1186/s12870-016-0743-2

Abstract

BackgroundFontainea picrosperma, a subcanopy tree endemic to the rainforests of northeastern Australia, is of medicinal significance following the discovery of the novel anti-cancer natural product, EBC-46. Laboratory synthesis of EBC-46 is unlikely to be commercially feasible and consequently production of the molecule is via isolation from F. picrosperma grown in plantations.Successful domestication and plantation production requires an intimate knowledge of a taxon’s life-history attributes and genetic architecture, not only to ensure the maximum capture of genetic diversity from wild source populations, but also to minimise the risk of a detrimental loss in genetic diversity via founder effects during subsequent breeding programs designed to enhance commercially significant agronomic traits.ResultsHere we report the use of eleven microsatellite loci (PIC = 0.429; PID = 1.72 × 10−6) to investigate the partitioning of genetic diversity within and among seven natural populations of F. picrosperma. Genetic variation among individuals and within populations was found to be relatively low (A = 2.831; HE = 0.407), although there was marked differentiation among populations (PhiPT = 0.248). Bayesian, UPGMA and principal coordinates analyses detected three main genotypic clusters (K = 3), which were present at all seven populations. Despite low levels of historical gene flow (Nm = 1.382), inbreeding was negligible (F = -0.003); presumably due to the taxon’s dioecious breeding system.ConclusionThe data suggests that F. picrosperma was previously more continuously distributed, but that rainforest contraction and expansion in response to glacial-interglacial cycles, together with significant anthropogenic effects have resulted in significant fragmentation. This research provides important tools to support plantation establishment, selection and genetic improvement of this medicinally significant Australian rainforest species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0743-2) contains supplementary material, which is available to authorized users.

Highlights

Fontainea picrosperma, a subcanopy tree endemic to the rainforests of northeastern Australia, is of medicinal significance following the discovery of the novel anti-cancer natural product, EBC-46
(3) Within the context of the low levels of genetic diversity and weak genetic structure observed for this species, two putative long-term refugial areas were identified in the eastern (Boonjie) and western (Evelyn Highlands) parts of the natural distribution of the species, which align with the refugial rainforest areas of Bartle-Frere Uplands and western Atherton Uplands identified by Hilbert et al [25]
We investigated the levels and partitioning of genetic variation across the known range of F. picrosperma and found that the seven populations surveyed were genetically distinct despite having uniformly low levels of genetic diversity

Summary

Introduction

A subcanopy tree endemic to the rainforests of northeastern Australia, is of medicinal significance following the discovery of the novel anti-cancer natural product, EBC-46. Of the more than 1000 drugs of novel chemical structure (New Chemical Entities) approved for use by international regulatory authorities between 1981 and 2010; greater than 60 % were derived from natural products [12]. The tropical rainforests of Queensland are inscribed on UNESCO’s World Heritage list and contain a substantial proportion of Australia’s rainforest biota As such, they are generally recognised as one of the continent’s main hotspots of biodiversity [10, 25, 51] with high levels of endemism due to ~35 million years of geographic isolation and considerable climatic change during the Tertiary [13, 26]. Fontainea picrosperma C.T. White (family Euphorbiaceae), a dioecious subcanopy tree endemic to Queensland’s tropical rainforests, illustrates the opportunity for continuing discovery of novel pharmaceuticals from nature and the value in protecting Australia’s mega-diverse rainforest flora

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