Trial translocations of Leionema equestre on Kangaroo Island, South Australia

Summary

Leionema equestre, a dwarf shrub endemic to Kangaroo Island, South Australia, survives as roadside populations threatened by weeds and road maintenance, with an estimated 2,600 plants confined to a small area between D'estrees Bay and Nepean Bay. Listed as Endangered, the species regenerates mainly after land clearance or bushfire, which also invites weeds into the small remnant stands. Starting in 1992, researchers trialled a translocation to Beyeria Conservation Park, about 4 km from the nearest wild population, to establish a new, protected population and test how herbivores and propagule type affected establishment. At three sites with differing soil types, pre-treated seed was direct-sown into cleared quadrats, with wire baskets protecting some seedlings from browsing. Germination peaked within four months, at 39-62% depending on site, then declined steadily; by 2009, only 1-5% of sown seed remained as surviving seedlings, and every survivor was growing inside a herbivore-exclusion basket. Three consecutive years of severe drought from 2006 to 2008 accelerated the decline. The trial ran for 18 years, tracking survival, flowering, reproduction and recruitment, and demonstrated that herbivore protection was essential to establishment on Kangaroo Island, while unprotected seedlings rarely persisted.