Conservation introduction of the Corunna daisy at Iron Knob, South Australia

Summary

The Corunna daisy (Brachyscome muelleri), Critically Endangered and restricted to a single 0.03 km2 site on cliff-foot slopes near Iron Knob, South Australia, unprotected and exposed to feral goats and rabbits, was introduced to a second site 1.5 km away with similar soil and vegetation but no historical record of the species, to spread extinction risk through a new satellite population. In September 1997, six-week-old nursery-raised seedlings were planted in replicated grid quadrats at both the new site and a control plot within the natural population, with annual recruitment counts continuing for 17 years and, at the new site, tracking of how far new recruits spread from the original planting point. Monitoring found abundant first-winter germination followed by a decline over the next two years, then a recurring three-to-four-year boom-and-bust recruitment cycle that peaked at about 450 seedlings in year eight and appeared unrelated to annual rainfall, with a similar pattern observed in the natural population; new recruits spread up to 15 metres downslope, consistent with short-range, gravity-and-water-assisted dispersal rather than any long-distance mechanism. In the last three years of monitoring, plant numbers declined as competing weeds increased. Difficulties included finding a second site with sufficiently similar conditions, the instability of steep, scree-covered slopes complicating fieldwork, and the species' limited natural dispersal capacity, which restricts expansion without human help. The project rates itself successful, crediting sustained flowering, seed set and natural recruitment at the new site over 17 years, and noting the new population reduces vulnerability to a single catastrophic event or genetic erosion.