Re-introduction of the endangered Bancroft’s Symonanthus in Western Australia

Summary

Bancroft's symonanthus (Symonanthus bancroftii), a low herbaceous shrub in the Western Australian wheatbelt, was considered extinct until a male plant was rediscovered in 1997 and a female in 1998; the female died in 1999 but both plants were preserved through in vitro tissue culture at Kings Park and Botanic Garden. The Botanic Gardens and Parks Authority translocated micropropagated plants into former mallee woodland habitat at two field sites, Ardath and Nangeen Hill Nature Reserve, from 2002 to 2007, with each plant numbered, irrigated one to two times weekly, and monitored. Early plantings during the 2002 to 2003 drought years had zero survival, but survival improved from 2004 onward once irrigation infrastructure using scheme water was secured. By October 2007, just over 250 plants survived across both sites, 211 at Ardath and 44 at Nangeen, including more than 120 seedlings planted that year. From 2005, seed collected from surviving plants allowed nursery-grown seedlings to supplement the more labour-intensive in vitro propagation. Major difficulties included habitat fragmentation, rabbit predation, weed invasion, and increasingly severe drought. The project explicitly rated itself Partially Successful, stating it has yet to demonstrate that seedling recruitment from the soil seed bank is feasible or that the reintroduced populations are stable and self-sustaining, despite the encouraging survival of translocated plants to date.