Ironstone Grevillia (Grevillia elongata) Interim Recovery Plan 2003-2008

Interim Recovery Plan no. 131
Gillian Stack and Val English
Department of Conservation and Land Management, WA, 2003

1. Background

History

The first collection of Grevillea elongata, housed at the Western Australian Herbarium, was made in 1950 by R. Royce. Further collections have since been made and there is currently a total of over 1,300 plants known from seven confirmed and one unconfirmed population.

An area of private land that contains Population 7 was purchased by the Department of Conservation and Land Management (the Department) in 1998. A second parcel of private land that contains over 100 healthy plants in Population 1e was purchased the following year. These areas have been fenced from stock and are now Nature Reserves.

An Interim Recovery Plan (IRP) was developed for the species in 1999 (Phillimore et al. 1999). Information collected since that plan was completed has been incorporated into this plan and this document now replaces Phillimore et al. (1999). This IRP will be implemented in conjunction with the IRP for the 'Shrublands on southern Swan Coastal Plain Ironstones' (English 1999), in which the species generally occurs, and with the plans for Petrophile latericola and Grevillea maccutcheonii that occur in the wider habitat of some populations.

Description

Grevillea elongata is a tall upright shrub to 2 m tall by 2.5 m wide with terete erect branchlets. The leaves are 2.5-5 cm long, glabrous and finely divaricate. The inflorescences are terminal or axillary, sessile or shortly pedunculate and white and cream in colour. The fruit is obliquely shaped, 8 mm long, 3.5 mm wide and 4 mm deep. The species was once thought to be a form of kerosene bush (G. paniculata) which has leaves channeled on the upper surface, smaller floral bracts (1 mm long), a globose conflorescence with shorter floral rachis (5 mm long), longer pedicels and deeply wrinkled fruits (Olde and Marriott, 1994).

Distribution and habitat

Grevillea elongata is endemic to Western Australia and is apparently confined to the Whicher Range area. The species is found on poorly drained soils ranging from red-brown gravelly clay over ironstone through light brown sandy clay over ironstone to grey sandy soils. It is largely confined to the threatened ecological community known as 'shrubland association on southern Swan Coastal Plain ironstones' ('Southern Ironstone') (Gibson et al. 1994; English 1999; English and Blyth 1997). G. elongata occurs in association with Corymbia calophylla, Dryandra squarrosa subsp. argillacea, Calothamnus sp. Whicher and Xanthorrhoea sp.

Critical habitat

Critical habitat is habitat identified as being critical to the survival of a listed threatened species or listed threatened ecological community. Habitat is defined as the biophysical medium or media occupied (continuously, periodically or occasionally) by an organism or group of organisms or once occupied (continuously, periodically or occasionally) by an organism, or group of organisms, and into which organisms of that kind have the potential to be reintroduced (Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)).

The critical habitat for G. elongata comprises:

  • the area of occupancy of known populations;
  • areas of similar habitat within 200 metres of known populations, i.e. shrubland on poorly drained soils in association with ironstone (these provide potential habitat for natural range extension);
  • corridors of remnant vegetation that link populations (these are necessary to allow pollinators to move between populations and are usually road and rail verges);
  • the local catchment area (the species occurs on seasonally wet soils which are dependent on the maintenance of local surface and ground water hydrology); and
  • additional occurrences of similar habitat that do not currently contain the species but may have done so in the past (these represent possible translocation sites).

Habitat critical to the survival of the species, and important populations
Given that this species is listed as Critically Endangered it is considered that all known habitat for wild and translocated populations is habitat critical.

Benefits to other species/ecological communities
Population 1 is located within an occurrence of a Threatened Ecological Community (TEC) listed as Endangered under the EPBC Act, and Critically Endangered in Western Australia. Petrophile latericola and Grevillea maccutcheonii (listed as Critically Endangered under the Wildlife Conservation Act 1950 and Endangered under the EPBC Act) also occur in the wider habitat of some populations of Grevillea elongata. Recovery actions implemented to improve the quality or security of the habitat of some populations of Grevillea elongata are likely to improve the status of the TEC in which this population is located, and also that of populations of other listed flora that occur in the wider habitat.

International Obligations
This plan is fully consistent with the aims and recommendations of the Convention on Biological Diversity, ratified by Australia in June 1993, and will assist in implementing Australia's responsibilities under that Convention. However, as Grevillea elongata is not listed under any international agreement, the implementation of other international environmental responsibilities is not affected by this plan.

Role and interests of indigenous people
There are no known indigenous communities interested or involved in the management of areas affected by this plan. Therefore no role has been identified for indigenous communities in the recovery of this species.

Social and economic impacts
Some populations of Grevillea elongata occur on private land and negotiations will continue with regard the future management of these populations. Recovery actions refer to continued liaison between stakeholders with regard these areas.

Evaluation of the Plan's Performance
The Department of Conservation and Land Management, in conjunction with the Recovery Team will evaluate the performance of this IRP. In addition to annual reporting on progress with listed actions and comparison against the criteria for success and failure, the plan is to be reviewed within five years of its implementation.

Habitat requirements: Grevillea elongata is endemic to Western Australia and is apparently confined to the Whicher Range area. It is found on soils ranging from red-brown gravelly clay over ironstone through light brown sandy clay over ironstone to grey sandy soils. It generally occurs in low, often very diverse heathland with Corymbia calophylla, Dryandra squarrosa subsp. argillacea, Calothamnus. sp Whicher and Xanthorrhoea sp.

Biology and ecology

Very little is known about the biology of the species. Many small beetles have been seen on the flowers and the species is believed to be insect-pollinated. Seed is probably dehisced soon after maturity, and this is typical for grevilleas. Longevity of the seed is unknown, as is the plant's life span. Grevillea elongata regenerates from seed after fire (Olde and Marriott, 1995).

Grevillea elongata seedlings have germinated within a second rotation on a pine plantation (Population 6), but it does not occur on the fire breaks. Subpopulations 6b and 6c occur adjacent to native bushland, however, only three plants have germinated within the bush area, and these occur along the track edge of the pine plantation. It appears therefore, that the species responds well to substantial soil disturbance and that seed is long lived.

Susceptibility of Grevillea elongata to the plant pathogen that causes dieback, Phytophthora cinnamomi, is unclear, but in general members of the family Proteaceae are highly susceptible. The occurrence of waterlogged soils in the habitat, and earth moving activity associated with maintenance of roads, firebreaks and pine plantations may predispose the species to the disease. Testing by The Department's Science Division indicates that Grevillea elongata germinants were not susceptible to P. cinnamomi under laboratory conditions (¹ C. Crane, personal communication). Testing of G. elongata for P. cinnamomi in the field however, has proved positive on two occasions (Subpopulations 6a and 6b). It may be, therefore, that the species is able to resist the disease when healthy but succumbs when under stress in the field. Further testing of Phytophthora cinnamomi susceptibility is required.

Threats

Grevillea elongata was declared as Rare Flora in 1996 under the Western Australian Wildlife Conservation Act 1950. It is listed as Endangered under both the Western Australian legislation and under the EPBC Act. It currently meets World Conservation Union (IUCN, 2000) Red List Category 'EN' under criteria C1 (IUCN 2000) due to the high level of fragmentation of populations, and a continuing decline in the quality of the habitat. The rarity of G. elongata is probably mainly due to clearing for agricultural purposes, particularly on heavier soils, that has occurred in the Busselton area. Over 90% of the highly restricted 'Southern Ironstone' community with which the species is generally associated, has been cleared (Tille and Lantzke 1990a, 1990b). The main threats are weed competition, inappropriate fire regimes, road, rail and firebreak maintenance activities, disease, pine plantation activities, mining, grazing and chemical drift.

  • Weed competition is a serious threat to Populations 1, 2, 3, 4 and 5. Populations 3 and 4 are very narrow linear populations immediately adjacent to cleared paddocks, and are already badly weed infested. They are threatened by both grasses and broadleaved weeds. Population 2 is a broader linear population, invaded mostly by Watsonia, with fewer grasses. Weeds suppress early plant growth by competing for soil moisture, nutrients and light. They also exacerbate grazing pressure and increase the fire hazard due to the easy ignition of high fuel loads, which are produced annually by many grass weed species.
  • Inappropriate fire regimes would adversely affect the viability of populations, as seeds of Grevillea elongata probably germinate following fire. If this is the case, the soil seed bank would rapidly be depleted if fires recurred before regenerating or juvenile plants reached maturity and replenished the soil seed bank. However, it is likely that occasional fires are needed for reproduction of this species.
  • Road, rail and firebreak maintenance activities threaten plants and habitat at all road verge and rail reserve populations of Grevillea elongata. These include actions such as grading the road verge, constructing drainage channels and mowing the roadside vegetation to improve visibility. These disturbance events also often encourage weed invasion.
  • Dieback disease is a moderate threat to all populations. Phytophthora cinnamomi causes the roots of infected plants to rot and results in death through drought stress. Grevillea elongata may be susceptible to P. cinnamomi when under stress. Populations occur in harsh environments within a pine plantation and on seasonally waterlogged ironstone soils and most of the habitat in which it grows is severely affected by dieback disease.
  • Plantation activities impact on Population 6. Activities that may threaten this population include fertiliser application, firebreak maintenance, tree harvesting and site preparation. In addition, competition for light, soil moisture and growing space will increase as the pine plantation matures.
  • Mining is not currently a direct threat to populations of G. elongata, however, minerals sands exploration and activity continues to occur in the region and may pose risk to populations in the future. Populations 1c and 1d occur on private property owned by a mining company, however, the populations are currently managed for conservation.
  • Grazing by rabbits, kangaroos or stock has impacted on many G. elongata populations. In addition to grazing, rabbits also impact on populations by encouraging invasion of weeds through soil digging, addition of nutrients to soil, and introduction of weed seeds. The high level of palatable weeds near these populations attract herbivorous animals, which are often unselective in their grazing.
  • Chemical drift from herbicide and fertiliser applications from nearby farmland may affect the species' growth and survival.

¹ Colin Crane - Phytophthora researcher, the Department's Science Division

Summary of population information and threats
Pop. No. & Location Land Status Year/No. plants Condition Threats
1a. SE Busselton Shire Road Reserve 1997 50+ Healthy Weeds, road maintenance, fire
1b. SE Busselton Rail Reserve 1997 100+ Healthy Weeds, rail maintenance, fire
1c. SE Busselton Private Property 1995 160 Healthy Fire, mining
1d. SE Busselton Private Property 1995 160 Healthy Fire, mining
1e. SE Busselton Nature Reserve 1995 100
1998 100+
1999 100
Healthy Weeds, disease, grazing
2a. SE Busselton Shire Road Reserve 1997 100+ Healthy Weeds, road maintenance, fire
2b. SE Busselton Rail Reserve 1997 100+ Healthy Weeds, rail maintenance, fire
2c. SE Busselton Shire Road Reserve 1997 100+ Moderate Weeds, road maintenance
2d. SE Busselton Rail Reserve 1997 100+ Moderate Weeds, rail maintenance
3a. SE Busselton Shire Road Reserve 1997 60+
1998 60
2002 40+ (10)*
Healthy Weeds, road maintenance
3b. SE Busselton Drain Reserve 1995 40
2002 *
Healthy Weeds
3c. SE Busselton Private Property 2002 20+ (2) Healthy Grazing
4. SE Busselton Shire Road Reserve 1996 44
1997 44
Moderate Weeds, road maintenance
5. SE Busselton Private Property 1997 3 Poor Weeds,grazing
6a. SE Busselton State Forest 1997 12
1999 15
2001 400+*
Mod/Poor Plantation operations, fire, dieback
6b. SE Busselton State Forest 1997 160
1999 97
2001 *
Poor Plantation operations, fire, dieback
6c. SE Busselton State Forest 1997 40
1999 25
2001 *
Moderate Plantation operations, fire
7. SE Busselton Nature Reserve 1999 2 Healthy Fire
#8. S of Duranilling To be determined 1983 infrequent To be determined To be determined

Numbers in brackets = number of juveniles. * = total for subpopulations combined. #Population requires confirmation of status.

Guide for decision-makers
Section 1 provides details of current and possible future threats. Any on-ground works (clearing, firebreaks, roadworks etc) in the immediate vicinity of Grevillea elongata will require assessment. On-ground works should not be approved unless the proponent can demonstrate that they will not have an impact on the species, its habitat or potential habitat, or on the local hydrology.