Split-Leaved Grevillea (Grevillea althoferorum) Interim Recovery Plan 2003-2008

Interim Recovery Plan No. 129
Gillian Stack and Val English
Department of Conservation and Land Management, WA, 2003

1. Background

History

Grevillea althoferorum was first collected south of Eneabba in 1978 by E.A. Griffin 1. This population was destroyed during mining operations and subsequent surveys by Griffin did not locate any additional populations. In 1991, P. Olde 2 discovered approximately 100 plants some 5 km east of the Griffin collections (Population 1). Departmental staff and consultants carried out subsequent surveys of the area during 1991-1994, but no further populations were located. A second population of 30 plants, occurring 200 km south of Population 1 was located during a floristic survey of the southern Swan Coastal Plain (Gibson et al. 1994).

An Interim Recovery Plan was developed for the species in 1999 (Hamilton-Brown and English 1999). Information collected since that plan was completed has been incorporated into this plan and this document now replaces Hamilton-Brown and English (1999).

Description

Grevillea althoferorum is a lignotuberous shrub with trailing stems up to 3 m long, and angular branchlets covered with very fine, long, soft hairs. Its leaves are 1.5 to 2 cm long, ascending to spreading, shortly petiolate and twice divided, lobes broadly triangular with recurved pungent points. The terminal inflorescence is 2 to 6 cm long and erect or decurved. The cream flowers (floral whorl and style) are regular (not one-sided), and the buds are covered in pinkish-brown hairs. The grooved, oblong fruit is 12 to 15 mm long and 3 to 4 mm wide.

It is closely related to Grevillea rudis but differs in that the leaves are more deeply divided to the midrib, and it has a shorter (generally not exceeding the leaves), denser inflorescence.

Distribution and habitat

Grevillea althoferorum is currently restricted to two known populations 200 km apart, one south of Eneabba and the other near Bullsbrook.

Population 1 is found on the crest of a low rise on pale brown loamy sand or grey sand supporting low heath. Grevillea althoferorum forms a part of the mid-dense shrub layer with Grevillea integrifolia, G. shuttleworthiana, Verticordia grandis, Viminaria juncea, Hakea prostrata and numerous other shrub species. The population occurs on a 12 m wide road verge and is threatened by weed invasion, road maintenance and agricultural activities, grazing, general ground disturbance by rabbits and foxes, and inappropriate fire regimes.

Population 2 occurs at the base of the Darling Scarp in greyish-yellow colluvial sand in Banksia low woodland. It forms part of the shrub layer in a Banksia menziesii and B. attenuata woodland with Hibbertia hypericoides, Xanthorrhoea preissii, Conostephium pendulum, other shrubs, and herb species. The population is in a conservation reserve adjacent to agricultural land. The reserve is known to contain dieback disease caused by the plant pathogen Phytophthora megasperma and the Grevillea althoferorum population is also at risk from firebreak maintenance, inappropriate fire regimes and possibly herbicide or fertiliser drift associated with agricultural activity on adjacent land.

Any future searches for the species and for possible translocation sites should be focused on both habitats described above, as both appear suitable for the species.

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 Grevillea althoferorum comprises:

  • the area of occupancy of known populations;
  • areas of similar habitat within 200 metres of known populations, i.e. low heath or woodland on lateritic sandy clay or yellow colluvial sand (these provide potential habitat for natural range extension);
  • 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).

1 Ted Griffin, botanist
2 Peter Olde, botanist and Grevillea specialist

Habitat critical to the survival of the species, and important populations

Given that this species is Critically Endangered it is considered that all known habitat is habitat critical. In addition all populations are considered important to the survival of the species as the two populations have been found to be genetically distinct.

Benefits to other species/ecological communities

A threatened ecological community (TEC) listed as Vulnerable in Western Australia the 'herb rich saline shrublands in clay pans' occurs adjacent to Population 2. Recovery actions implemented to improve the quality or security of the habitat of Grevillea althoferorum Population 2, such as control of dieback disease are likely to improve the status of this TEC.

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 althoferorum 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

There are not likely to be any major social or economic implications as a consequence of the implementation of this plan.

Evaluation of the Plan's Performance

The Department of Conservation and Land Management, in conjunction with the Recovery Teams 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.

Biology and ecology

It appears that there is a divergence in the reproductive biology of the two populations of this species. Neither population has shown recent evidence of seedling recruitment. Population 1 has been confirmed as clonal and is actively recruiting from root suckers. Population 2 does produce seed but at very low levels. Burne et al. (in press) found that 0.15% of flowers set fruit. In addition, they found that the lack of sexual recruitment in Grevillea althoferorum is most likely to be due to the lack of viable pollen on the stigmas, which was almost nil at Population 1 (Burne et al. in press).

Genetic work also suggests that both populations are clonal, with very little diversity within each, and substantial difference between populations (personal communication M. Byrne 3). Banksia goodii is a similarly rare resprouter that produces few seeds, for which any accidental losses of adult plants were found to increase the mortality rate and cause accelerated declines in population size (Drechsler et al. 1999; cited in Burne et al. in press).

The presence of root suckering at Population 1 and lignotubers at Population 2 indicates that Grevillea althoferorum resprouts following removal of above-ground plant material through disturbances such as fire or grazing (Burne et al. in press).

G. althoferorum is suspected to be susceptible to dieback disease.

Threats

Grevillea althoferorum is currently ranked Critically Endangered under World Conservation Union (IUCN, 2000) Red List criterion B2ab(iii) (IUCN 2000) as there are less than 300 adult plants known from two highly fragmented populations, with continuing decline in the quality of the habitat. The main threats are weeds, grazing, disease, road, track, fence and firebreak maintenance, inappropriate fire regimes and chemical drift.

  • Weed invasion is a major threat to Population 1. 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.
  • Grazing by rabbits (Oryctolagus cuniculus) and possibly kangaroos (Macropus spp.) and/or sheep has had a major impact on Population 1. In addition, disturbance of soil by rabbit warren and fox midden construction, increased nutrient levels from their droppings and the introduction of weeds are impacting the habitat of the species. Grazing may have an impact on the establishment of Grevillea althoferorum juveniles (seedlings or young ramets), thereby limiting natural recruitment.
  • Disease could be a serious threat to Population 2. Dieback, in this case believed to be caused by the plant pathogen Phytophthora megasperma, occurs in the immediate vicinity of Population 2. This plant pathogen causes the roots to rot and results in death from drought stress. It is suspected that G. althoferorum is susceptible to this pathogen. Even if not susceptible (some Grevilleas are not susceptible to Phytophthora spp.), the Banksia woodland habitat that occurs at this site is characteristically highly susceptible. Changes in the structure of the habitat caused by dieback, for example opening up of the canopy, may then impact on the G. althoferorum population.
  • Road, track and firebreak maintenance activities have threatened both populations in the past. Construction of drainage channels, grading and other road maintenance activities impact on road verge populations of G. althoferorum. Several of these actions also encourage weed invasion. Relevant authorities have been informed of the road reserve population and have been advised of the need for appropriate protective measures.
  • Fence maintenance activities are a potential threat to the roadside Population 1, in the event that the adjoining farmland boundary fence should need repair or replacement. This is not considered an immediate threat as the landholders have been made aware of the population.
  • Inappropriate fire regimes may affect the viability of populations, as Grevillea althoferorum resprouts after fire. The reserves of the lignotuber could be exhausted if fires recurred before plants could build up fresh reserves. However, it is likely that occasional fires would stimulate ramet production in this species.
  • Chemical drift from herbicide and fertiliser application on adjacent farmland may affect the species' growth and survival, particularly at Population 1. The owners of land adjacent to Population 1 have been informed of the species' presence, to prevent possible grazing, fire damage and agricultural chemical drift.
  • Lack of genetic diversity is evident within each population, affecting the evolutionary adaptability of this species. The populations may continue indefinitely if well adapted to their environmental conditions, but if those conditions change, the taxon may have limited ability to adapt.
Summary of population information and threats
Pop. No. & Location District Land Status Year/No. plants Condition Threats
1. S of Eneabba Moora Shire Road Reserve 1995 100
1999 75
2000 55 (5)
2001 147
Moderate Weeds, grazing, warren and midden construction, road and fence maintenance activities, fire, chemical drift
2. Bullsbrook Perth Hills Nature Reserve 1995 30
1997 100+
1999 151
Healthy Disease, inappropriate fire regimes, firebreak maintenance

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 althoferorum will require assessment. On-ground works should not be approved unless the proponents can demonstrate that they will not have an impact on the species, its habitat or potential habitat.