North Queensland Naturalist
North Queensland Naturalist 48 (2018): 57-68
Purple-flowered Wattle (Acacia purpureopetala): observations and surveys of a threatened plant found only in the Herberton-Irvinebank region
Simon J. Gleed and Donald C. Franklin
The Purple-flowered Wattle (Acacia purpureopetala) is the only wattle with purple or pink flowers. The species is known only from the Herberton-Irvinebank region in north Queensland, Australia. Its conservation assessment of Critically Endangered under Commonwealth legislation has been based on an estimated total population of 500 individuals in 10 ‘populations’ with an area of 8.6 hectares. Over six years, we examined 24 patches of A. purpureopetala, 21 with either population counts and measurement of patch area or estimates of these. We provide a morphological description of the species, notes on reproduction, an updated estimate of the total population, number of sub-populations and area occupied, and notes on site characteristics. The Purple-flowered Wattle is a small shrub with limited root development, sparse and diffuse flowering and seed set, and evidently limited capacity for seed dispersal. In 21 patches, we conservatively estimate there to be just over 7,000 adults in patches summing to 20.4 hectares. Patches occur in a diversity of landscape settings but consistently on harsh sites with a sparse grass layer, this and other evidence suggesting that the species is an obligate seeder intolerant of frequent fire. Infrequent disturbance such as grading of firebreaks and mining appears to have promoted establishment of individuals in some patches, but many patches lack any current or obvious historic disturbance. Purple-flowered Wattle is known from 16 sub-populations with an Extent of Occurrence of 634 km2. Notwithstanding the increased population estimate, Purple-flowered Wattle remains an extremely rare species whose conservation warrants high-level consideration.