Rarity and threat in relation to the conservation of Acacia in Western Australia
Marcelle L. Buist*1,2, David J. Coates1 and Colin J. Yates1
(1) Science Division, Department of Conservation and Land Management, Locked Bag 104, Bentley Delivery Centre, Western Australia 6983
(2) Department of Soil Science and Plant Nutrition, School of Earth and Geographical Sciences, University of Western Australia, Nedlands, Western Australia 6907 (*corresponding author)
The genus Acacia provides clear illustrations of both the floristic diversity of Western Australia (with nearly 800 of the 1200 known taxa found in the State) and the critical conservation status of a significant component of the flora. Twenty-six percent of acacias in W.A. are either listed as threatened (Declared Rare Flora) or rare and poorly known (Priority Flora). This paper explores rarity and threat in relation to the conservation of Acacia in W.A. Rarity is ascertained using the three components of geographical range, habitat specificity and abundance. The factors which then pose immediate threats to survival of the taxon are identified to determine the likelihood of population persistence and further priorities for conservation. The threats include invasive flora and fauna, inappropriate fire regimes, habitat destruction associated with clearing activities, alteration of hydroecology, and demographic and genetic effects associated with small declining populations. These threats are also identified to impact on the persistence of rare acacia taxa. Understanding the ecological and genetic consequences of rarity in terms of low numbers of small, often fragmented populations can provide vital clues to the development of management actions and conservation strategies for rare and threatened species. A particularly effective approach to understanding rarity and its implications for conservation is to carry out comparative reproductive, genetic and ecological studies on the rare species and closely related more common species. This approach and single species studies are included in this review to provide examples of how ecological and genetic research can lead to an understanding of the factors that may constrain population’s persistence. Our conclusions are that, like the rest of the flora, most rare and threatened Acacia taxa occur in W.A.’s Wheatbelt where there has been extensive habitat alteration. In this region the presence of relictual taxa, complex patterns of genetic diversity, highly fragmented remaining native vegetation, small plant population sizes and introduction of invasive weeds and herbivores makes conservation management a complex task. We show that basic and applied research into rarity and threat in Acacia can provide valuable information for the conservation of this large, diverse genus.