Grevillea scapigera, a 30-year journey of recovery

Dr Siegy Krauss (Research Scientist)

The vital contribution of Kings Park to The Decade is built on many decades of research and practise in the recovery of native species and degraded ecosystems.

The extraordinary story of the critically endangered Corrigin Grevillea is a flagship example. First collected in 1954, it has only ever been known from a handful of small, mainly degraded, roadside populations within 50 km of the Wheatbelt town of Corrigin.

The delicate insect pollinated flower of the Corrigin Grevillea, Grevillea scapigera. Photo: Siegy Krauss

The Corrigin Grevillea was presumed extinct in 1986, a consequence of broadscale destruction of its habitat for agriculture.

In 1989 a single grafted plant was identified at the Royal Botanic Garden in Sydney, which was brought to Kings Park and initiated successfully into in vitro culture. The following year naturally occurring plants were rediscovered near Corrigin. Only 35 specimens were known in the wild at the time.

A translocation was determined to be essential for the survival of the species. The aim was to re-establish at least three self-sustaining populations in the wild to improve its conservation status. In situ conservation efforts were underpinned by the establishment of a secure ex situ collection, where 25 wild genotypes are maintained in cryopreservation and tissue culture at Kings Park.

Corrigin Grevillea, Grevillea scapigera, in ex situ tissue culture collection at Kings Park. Photo: Siegy Krauss

A key step was the appointment of a recovery team which included Bob Dixon from Kings Park, staff from the (then) WA Department of Conservation and Land Management (CALM), the Australian Nature Conservation Agency and members of the local community. The voluntary involvement and enthusiasm of the community, led by the amazing Robin Campbell in Corrigin, Kings Park volunteers and the Corrigin Landcare group which includes local farmers, has been critical.

In the early 1990s, secure translocation sites were identified within the last remaining native vegetation remnants and fenced to exclude rabbits. Plantings of around 425 seedlings were initially carried out between 1993 and 1998 under strict phytosanitary guidelines.

Bob Dixon monitors tagged plants of Grevillea scapigera at the Corrigin airstrip translocation site. Photo: Siegy Krauss

Seedlings were propagated by tissue culture from ten wild plants, as seeds were not able to be germinated. In 1999, a genetic study showed over half of all plants were from a single clone. This was addressed by increasing the number of clones from tissue culture and introducing additional wild plants.

Plantings occurred in following years, largely from seed harvested on site, once dormancy issues were resolved. Flowering and natural seed set has been very high and some natural recruitment occurred in most years.

Plants were again genetically monitored in 2007, 2012 and 2018 which showed that measures implemented to stabilise the erosion of genetic diversity have been successful, with genetic diversity increasing in third generation plants. Genetic results highlighted that rapid genetic erosion may be a feature of many small, translocated populations that without attention may ultimately threaten their longterm survival.

Siegy Krauss monitors Grevillea scapigera, Corrigin airstrip translocation site. Photo: Robin Campbell

Hundreds of adult plants have been established in secure, threat-free sites. In most years, plants have flowered heavily and attracted large numbers of insect pollinators, resulting in abundant seed set, estimated in many years to exceed one million seeds. Seed now persists in the soil-stored seed bank and burial trials show seed viability remains very high after many years.

In 2014, for example, almost all of an estimated 455 individuals across all translocation sites were the result of in situ germination of soil-stored seed. In 2021 only 50 plants remain, reflecting particularly harsh drought conditions over recent years and the naturally ephemeral nature of wild populations, where individual plants typically live for up to eight years. Knowledge of the extensive soil-stored seed bank, however, suggests that appropriate disturbance (naturally, fire) will stimulate a mass germination response.

The floristically diverse Grevillea scapigera translocation site at Corrigin airstrip in 2018. Photo: Siegy Krauss

The original aim, which was to establish three self-sustaining translocated populations, was met within 20 years. Sites have not been actively managed for several years but appear to be self-sustaining, in part because local species are outcompeting weeds.

All sites are well vegetated and species richness of flora and fauna continues to increase. Ultimately, the lessons learnt from this highly successful recovery of the Corrigin Grevillea highlights the important work of Kings Park and underpins future success stories in this forthcoming Decade on Ecosystem Restoration.