Morphometric, genetic and ecological studies clarify the conservation status of a rare Acacia in Western Australia

Abstract

Acacia species 'Dandaragan' is known from one population confined to the Dandaragan–Badgingarra area in south-western Western Australia and is classified as critically endangered. Morphological and allozyme studies show that A. sp. 'Dandaragan' has close affinities with Acacia microbotrya Benth. sens. lat. and warrants taxonomic recognition at subspecies rank. A combination of floral and phyllode characters clearly separated A. sp. 'Dandaragan' and A. microbotrya s. l. by the presence of a discrete morphological boundary in the canonical variates plot and the high percentage of correct re-substitution classifications of individuals into pre-defined taxa. UPGMA and maximum likelihood analyses of allozyme data distinguished A. sp. 'Dandaragan' and A. microbotrya s. l. Levels of genetic diversity were lower in A. sp. 'Dandaragan' than in A. microbotrya s. l. The size-class and lifestage structure of the A. sp. 'Dandaragan' suggests that the population is stable and possibly increasing in size predominantly by vegetative spread. The presence of a soil seed reserve and the ability to reproduce from root suckers suggests that A. sp. 'Dandaragan' is resilient to fire. Levels of innate seed dormancy were lower and tolerance to thermal shock higher in A. sp. 'Dandaragan' compared with A. microbotrya s. l. The population size, structure and germination ecology suggest that A. sp. 'Dandaragan' does not appear to have any immediate management requirements, apart from continued monitoring of adult plant health and recruitment. The study confirms that A. sp. Dandaragan should be recognised as Declared Rare (threatened) Flora and we recommend that the taxon's conservation status be reviewed.