Whorled eremophila (Eremophila verticillata) Interim Recovery Plan 2003-2008

Interim recovery plan no. 142
Robyn Phillimore and Andrew Brown
Department of Conservation and Land Management, WA, 2003

1. Background

History

J. Wrigley made the first known collection of Eremophila verticillata (housed at the South Australian Herbarium) from near Newdegate in 1968. In 1980, P. Luscombe made a collection of the species (Population 4), which is also housed at the South Australian Herbarium, from private property between Kalgarin and Pingaring. Although this second population was found on a similar soil type and geological formation as the first, plants were morphologically slightly different, with very hairy branches and leaves that were grey in appearance (personal communication B. Chinnock ¹ ). The plants were located in an area of land that, at the time, was being prepared for cropping and which resulted in the destruction of the population. No plants have been located in that area since.

In 1987 a population consisting of around 2000 plants (Population 2) was discovered by DCLM staff from Katanning District. The population was located in a strip of topsoil that had been redistributed following dolomite mining. At the time, the site was under a mining and grazing lease. The grazing lease expired in December 1989 and has not been renewed. The mining lease is still current and expires in 2004, but is renewable.

Eremophila verticillata is currently known from two extant populations containing a total of around 567 mature plants. Surveys for plants in the area of three old populations (Populations 3, 4 and 5) have proven unsuccessful and all three are currently presumed extinct.

Description

Eremophila verticillata is a small shrub to 1 m high and 80 cm across. Its erect or spreading branches are nearly cylindrical in cross-section. The lower section of the branches may be bare of leaves on mature plants. The leaves are fleshy, stalkless, green to purplish, in whorls of 3 and are pressed against the branches. They are a narrow oblong in shape, 2.5 to 6 cm long by 1 mm wide. The flowers are tubular, violet and have a white interior with purple spots. The outside of the corolla is covered with soft hairs. The fruits are dry, egg-shaped, 2 to 3 mm long by 1 to 2.5 mm wide, beaked, slightly separated at the apex and covered with feather-like hairs (Brown et al. 1998).

Eremophila verticillata is closely related to E. ternifolia but differs in its smaller, narrower, appressed leaves and different shaped fruit, in which the carpels are neither unequal or free in the upper half (Chinnock 1986).

Distribution and habitat

Eremophila verticillata is endemic to Western Australia where it is apparently confined to the Lake Cobham area. Habitat is powdery brown loam over dolomite in open low Eucalyptus woodland of E. longicornis (Morrell), E. annulata and E. flocktoniae (Merrit) over Maireana erioclada and Threlkeldia diffusa (Chinnock 1986). Other associated species include Melaleuca thyoides, Dodonaea concinna and Enchylaena tomentosa.

Biology and ecology

Eremophila is endemic to Australia and is represented in all mainland States. Currently, there are some two hundred named species and many unnamed ones. While most occur in semi-arid and arid regions, they are found in a range of habitats over a wide area. Eremophila species are not found in the high rainfall south-west corner of Western Australia. The plants are commonly referred to as emu bushes or poverty bushes.

The pollinator of Eremophila verticillata is unknown, although cabbage butterflies (Pieris rapae) have been observed feeding on the flowers.

A prescribed burn was undertaken at Population 1 by Departmental Science Division and Katanning District staff in 1994, as part of a study on six Eremophila species. Ten mature, senescing plants were burnt. Monitoring of the burn site in June 1995 by staff from DCLM's Katanning District recorded 13 seedlings with an average height of 5 cm, most occurred close to parent plants. One seedling was located 13 m away from the nearest possible parent, but was still within the burn area. Seven plants currently remain at this site. No epicormic growth was observed, suggesting that the species is killed by fire and regenerates only from soil-stored seed. A visual assessment of the relative density of the starch grains within the roots did, however, result in a visual starch rating of six, suggesting the species may also possess some characteristics of a resprouter (Richmond and Coates 1995).

¹ Bob Chinnock, Botanist, The Botanic Gardens of Adelaide and State Herbarium

Threats

Eremophila verticillata was declared as Rare Flora in September 1987 and ranked as Critically Endangered In September 1998. It currently meets World Conservation Union Red List Category 'CR' under criteria A2c, B1a,b(ii,v)+2a,b(ii,iv) and C1 due to its small area of occupancy, low number of plants, a decline in the number of populations and a decline in area and quality of habitat (IUCN 2000). The main threats are mining (extraction of dolomite), poor recruitment, competition from associated native species and weeds, vehicle damage, salinity, road maintenance and inappropriate fire regimes.

  • Extraction of dolomite is a possible future threat to one population of Eremophila verticillata. The mining lease on the area of Population 2 expires in 2004 and is renewable.
  • Poor regeneration, due to lack of appropriate disturbance, threatens both populations. Mature plants are beginning to senesce and very few young plants have been observed in recent years.
  • Competition from a dodder species (Cassytha sp.) is a minor threat to Population 2. Dodder covers some adult plants, competes for light, nutrients and possibly pollinators and physically restricts the Eremophila.
  • Vehicular damage has occurred to some plants at Population 2. The placement of a barrier at the site was deemed impractical due to the likelihood of vehicles driving around it. Liaison will continue to ensure that further damage does not occur (Recovery Action 11). If deemed necessary, fencing will be considered.
  • Weed invasion is a major threat to Population 2 and a minor threat to Population 1. The area containing Population 2 has been mined in the past and has been part of a grazing lease. The resulting disturbance has encouraged a proliferation of weeds at the site. 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.
  • Salinity is a possible future threat. Both populations occur near a salt lake and some signs of increasing salinity, including the death of some native vegetation and an increase in salt-tolerant species, is evident. Monitoring of both populations is required.
  • Road maintenance is a possible future threat to Population 1. Construction of drainage channels, soil movement and road widening may impact on the population. Relevant land managers have been informed of the location of the population and the threatened status of the species.
  • Inappropriate fire regimes may affect the long-term viability of populations. Adult plants of Eremophila verticillata are likely to be killed by fire, with recruitment from soil-stored seed. The soil seed bank would be depleted if fires occur before these juvenile plants reach maturity. Appropriate fires that occur a number of years apart are likely to be required for the species to regenerate. Further investigation is required and will be addressed in Recovery Action 15.
Summary of population information and threats
Pop. No. & Location Land Status Year/No. plants Condition Threats
1. W of Lake Cobham Unallocated
Crown Land
1980 60
2001 7
Moderate Road maintenance, mining, salinity, weeds, inappropriate fire regimes
2. NW of Lake Cobham Unallocated
Crown Land
1991 2000
2000 560+ [80+ dead]
Moderate Weeds, mining, competition, senescence and poor recruitment, salinity, inappropriate fire regimes
3. NW of Lake Cobham Unallocated
Crown Land
1980 3
1986 0
Presumed extinct  
4. S of Karlgarin Private Property 1980 1 hectare of healthy plants
2000 0
Presumed extinct  
5. E of Newdegate Unallocated
Crown Land
Unknown Presumed extinct  

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 Eremophila verticillata comprises:

  • the area of occupancy of the known populations,
  • areas of similar habitat ie. powdery brown loam in open low Eucalyptus woodland of E. longicornis, E. annulata and E. flocktoniae, within 200 metres of known populations (these provide potential habitat for natural recruitment),
  • corridors of remnant vegetation that link populations (these are necessary to allow pollinators to move between populations),
  • the local catchment which provides the correct water table for the species (the species occurs adjacent to a lake and is dependent on maintenance of local surface hydrology),
  • additional occurrences of similar habitat, ie. powdery brown loam in open low Eucalyptus woodland of E. longicornis, E. annulata and E. flocktoniae that do not currently contain the species (these represents possible future translocation sites).

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

Given that this species is listed as threatened it is considered that all known habitat is habitat critical. In addition, all populations, including translocated populations, are considered important to the survival of the species.

Benefits to other species/ecological communities

All populations are located within an area of low Eucalyptus woodland adjacent to a small lake. Recovery actions implemented to improve the quality or security of the habitat of Eremophila verticillata populations will improve the status of the remnant vegetation in which the populations are located.

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 Eremophila verticillata 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

The implementation of this recovery plan is unlikely to cause significant adverse social and economic impacts. However, a current mining lease near the area of one population expires in 2004, but is renewable, and it is possible that the protection of this species will have some minimal impact on the extraction of dolomite.

Evaluation of the Plan's Performance

The Department of Conservation and Land Management, in conjunction with the Katanning District Threatened Flora Recovery Team will evaluate the performance of this Interim Recovery Plan. The plan is to be reviewed within five years of its implementation. Any changes to management / recovery actions will be documented accordingly.

Guide for decision-makers

Section 1 provides details of current and possible future threats. Developments or on-ground works in the immediate vicinity of the population or within the defined critical habitat of Eremophila verticillata require assessment. No developments should be approved unless the proponents can demonstrate that they will not have a significant impact on the species, or its habitat or potential habitat, or the local surface and ground water hydrology.