Australasian Plant Conservation (formerly Danthonia)

Originally published in Danthonia 7(4), March 1999

Acacia whibleyana and Brachycome muelleri: Conservation Biology Reports for Two Endangered Species from South Australia's Eyre Peninsula

Dr Manfred Jusaitis, Plant Biodiversity Centre, Adelaide, and Trudy O'Connor, Student Botanical Intern, Centre for Plant Biodiversity Research, Canberra.

Both Brachycome muelleri and Acacia whibleyana are listed as nationally endangered, and endemic to small areas on South Australia's Eyre Peninsula. Black Hill Flora Centre have recently published two reports on these species as part of the Australian National Parks and Wildlife Service Endangered Species Program; Conservation Biology of Acacia whibleyana by Manfred Jusaitis and Birgitte Sorensen, and Conservation Biology of Brachycome muelleri, by Jusaitis, Sorensen and Lesley Polomka. Each of these focuses on one species, its ecology and biology, threatening factors, propagation and management recommendations.

Acacia whibleyana, The Whibley Wattle, is a dense shrub which grows to 2.5 metres in height and 4 metres diameter. While inconspicuous for much of the year, during the spring flowering season it is covered with golden spherical inflorescences typical of the Acacia genus. This species has a very restricted distribution, being found only in an area near Tumby Bay on South Australia's Eyre Peninsula. It has been rated by International Union for Conservation of Nature and Natural Resources (IUCN) criteria (1994) as being Critically Endangered.

Surveys undertaken as part of this project located a total of 322 plants in two separate populations. Most of these individuals were in somewhat disturbed areas, including roadside verges, a disused quarry and on grazed land. Study methods included vehicle-based surveys, soil collection and description and measurement of plant growth, flowering, seed production and dispersal. In addition, photopoints were established, plots seeded and seedling translocation techniques trialed. Due to the presence of plants near a salt lake, salt tolerance was also studied. It was found that the populations were threatened by human interference, as well as by weed invasion. Weeds reduced both the germination and growth rates of A. whibleyana.

Flowering and seed production were quite variable, while the soil seed bank was fairly poor, possibly due to seed predation. Seeds were dispersed by ants, attracted by the fatty aril attached to the seed. Germination trials suggested that scarification of the seeds using a sharp blade or boiling water were effective treatments in achieving high rates of germination. During this study conservation activities included fencing of the main population, spraying of weeds and translocation of plants. Plans for future conservation activities include the control of weeds, and plant translocations to connect roadside populations, as well as the establishment of an ex situ seed bank. Community involvement and education have also been identified as playing important roles in the protection of this very localised species.

Brachycome muelleri, the Corunna daisy, is another critically endangered plant species with a very restricted distribution on the Eyre Peninsula. While early collections were made in several South Australian locations, including the Para River, near Gawler and on the Yorke Peninsula, recent collections indicate that the pastoral property Corunna, on the upper Eyre Peninsula now has the only remaining stand of the species. The plant grows on steep south-facing cliff-foot slopes of the Baxter Hills, approximately 5 km from Iron Knob. The plant is an annual, germinating after autumn rains. It grows leaves in a rosette arrangement and reaches a height of up to 20 centimetres when in flower.

Brachycome muelleri flowers from late winter to spring, with white florets held above the rosette of leaves. This plant would appear to be in a precarious situation, due to its very restricted distribution, leaving it vulnerable to catastrophic events. Grazing by domestic stock, as well as feral goats and rabbits also constitute potential threats, and the species is not represented in conservation parks. The land manager has instigated an ongoing program of goat control and kangaroo culling. As part of this study, a second population of B. muelleri was translocated to a suitable new site on the western edge of the Baxter Hills. This translocation appears to have been successful, with natural regeneration occurring at the site one year after translocation. The report recommended further targeted surveys and translocations be undertaken, and that weed and animal effects on the original and new populations continue to be monitored to ensure populations remain sustainable. However, because of the extremely delicate nature of the soil substrate at the population sites, it was recommended that recovery actions be handled by small teams of hand-picked experienced people.

References

IUCN (1994). IUCN Red List Categories. IUCN Species Survival Commission. Gland, Switzerland.

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