Biodiversity

Species Profile and Threats Database


For information to assist proponents in referral, environmental assessments and compliance issues, refer to the Policy Statements and Guidelines (where available), the Conservation Advice (where available) or the Listing Advice (where available).
 
In addition, proponents and land managers should refer to the Recovery Plan (where available) or the Conservation Advice (where available) for recovery, mitigation and conservation information.

EPBC Act Listing Status Listed as Endangered
Listing and Conservation Advices Commonwealth Conservation Advice on Acacia imitans (Threatened Species Scientific Committee (TSSC), 2008aeb) [Conservation Advice].
 
Commonwealth Listing Advice on Acacia imitans (Threatened Species Scientific Committee (TSSC), 2008aeg) [Listing Advice].
 
Recovery Plan Decision Recovery Plan required, the species is known from six subpopulations with a low number of mature individuals. The species does not occur in any formal conservation reserves and most of the known localities are not being managed for conservation purposes. The species is subject to significant ongoing threats which can be better managed with a recovery plan in place (19/12/2008).
 
Adopted/Made Recovery Plans Acacia imitans Interim Recovery Plan 2009-2014 (Department of Environment and Conservation, 2010a) [Recovery Plan].
 
Other EPBC Act Plans Competition and land degradation by unmanaged goats (Department of the Environment, Water, Heritage and the Arts (DEWHA), 2008ada) [Threat Abatement Plan].
 
Federal Register of
    Legislative Instruments
Inclusion of species in the list of threatened species under section 178 of the Environment Protection and Biodiversity Conservation Act 1999 (69) (19/12/2008) (Commonwealth of Australia, 2008d) [Legislative Instrument].
 
State Government
    Documents and Websites
WA:Declared Rare or Poorly Known Flora in the Geraldton District (Patrick, S.J., 2001) [State Species Management Plan].
State Listing Status
WA: Listed as Critically Endangered (Wildlife Conservation Act 1950 (Western Australia): September 2013 list)
Scientific name Acacia imitans [65211]
Family Fabaceae:Fabales:Magnoliopsida:Magnoliophyta:Plantae
Species author Maslin
Infraspecies author  
Reference Maslin, B.R. (1999) Nuytsia 12: 356
Distribution map Species Distribution Map

This is an indicative distribution map of the present distribution of the species based on best available knowledge. See map caveat for more information.

Illustrations Google Images
http://florabase.calm.wa.gov.au/browse/profile/14118

The current conservation status of the Gibson Wattle, Acacia imitans, under Australian and State Government legislation, is as follows:

National: Listed as Endangered under the Environment Protection and Biodiversity Conservation Act 1999.

Western Australia: Listed as Declared Rare Flora under the Wildlife Conservation Act 1950.

Scientific Name: Acacia imitans

Common Name: Gibson Wattle

The Gibson Wattle is a low shrub that grows 0.2–1 m tall and to 3 m wide. This species has a semi-prostrate (spreading) habit and a dense canopy with intricate and dense branching. Branches are grey, glabrous and smooth, dividing into numerous, short, straight, rigid divaricate and spinescent branchlets, often devoid of phyllodes. Phyllodes are asymmetric, small and have a sharp, upturned point. Inflorescences are simple on a 3–4 mm long peduncle, flowering heads are yellow, obloid to shortly cylindrical, 6–8 mm long and 4–5 mm in diameter. Flowering occurs from August to September (Maslin 1999).

The Gibson Wattle is endemic to Western Australia and is known from six subpopulations in the Mount Singleton area approximately 300 km north-east of Perth (WA CALM 2006). Four subpopulations are known to occur at Ningham Station and two at Mount Gibson Station.

The extent of occurrence is estimated to be approximately 20 km² (TSSC 2008aeb). A dataset taken from the Western Australian Department of Environment and Conservation's Threatened Flora Database (which contains a single GPS coordinate for each subpopulation) was used to determine the area of occurrence. There is no data available to indicate a decline in extent of occurrence of this species (WA CALM 2006).

There is insufficient data to calculate the actual area of occupancy of the Gibson Wattle and the area of occupancy is likely to be considerably less than the extent of occurrence. Area of occupancy was measured for three subpopulations in 2001, however follow-up surveys were not conducted and area trends cannot be established (TSSC 2008aeg).

Despite the limited availability of data, it is predicted that subpopulations are likely to reduce due to a lack of comprehensive feral goat (Capra hircus) mitigation (WA CALM 2006). Feral goat culling is occurring in limited capacity over the distribution of the Gibson Wattle, however, the success of this program in the recovery of this species is uncertain.

The species distribution is not considered to be fragmented as subpopulations are confined to the slopes and summit of Mount Singleton Range (WA CALM 2006).

Staff from the Western Australian Herbarium have conducted surveys for Gibson's Wattle in the Mount Singleton and Mount Gibson area in 1992, 1993, 1994, 1996 and 2001. These surveys have been conducted at different times of the year, generally during the flowering period, with different field survey periods, from 0.5 days to 3 days. The Department of Conservation and Land Management conducted surveys in 2002, 2003 and 2004 (WA CALM 2006).

The total number of individuals for the Gibson Wattle is estimated to be 550 mature plants across six recorded subpopulations (WA CALM 2006). The greatest distance between these subpopulations is approximately 15 km. All subpopulations are considered necessary for the recovery and long-term survival of this species (WA CALM 2006).

Subpopulations 1, 4a and 4b have increased in numbers due to more plants becoming recognisable, plants presumed dead showing new growth and greater survey effort (TSSC 2008aeg). Subpopulation 3 has remained stable, subpopulation 5 has experienced a decline to 80+ plants and subpopulation 1 has increased over time: the reasons for these patterns are unknown, but may be linked to natural factors or surveying anomalies (WA CALM 2006). There are no records for subpopulation 2 after 1994 and no plants were found for subpopulation 6 in 2004 (WA CALM 2006).

The following table presents survey results at known subpopulations:

Subpopulation Year Number of mature plants
1 1992
1993
2001
2002
2003
2004
100+
100+
51
50+
50+
200+
2 1994
The subpopulation has not been surveyed since 1994. There is some uncertainty regarding this subpopulation as the specimen collected showed characteristics of A. kochii. This issue is yet to be resolved.
10+
3 2001
2002
2003
2004
30
21
20+
30+
4a & 4b 2001
2002
2004
30
36
200+
5 2001
2002
2004
118+
80+
80+
6 2001
2003
2004
30
30
None found

Althouth there are insufficient data to demonstrate a decline in the Gibson Wattle, the pattern of mortality from feral goat browsing suggests a long-term downward trend (TSSC 2008aeg). Also, the structure of populations, occuring as cohorts of less than 200, suggests potential localised extinction from stochastic events (TSSC 2008aeg).

No cross breeding has been recorded for this species.

None of the known subpopulations are located in reserve systems. Subpopulations in the Ninghan Station region are in leased pastoral land, however Mount Gibson Station has been leased to a private conservation group who has begun destocking the station (WA CALM 2006). Two subpopulations are found on Mount Gibson Station. The impacts of destocking to date are that new growth is being recorded and declining goat numbers. Grazing is still evident but exerts less pressure than previous years.

The Gibson Wattle grows on slopes in rocky red loam derived from dolerite, in tall shrubland. Some plants have been observed to grow in mixtures of red loam and dolerite (WA CALM 2006).

The Gibson Wattle flowers between August and September. The biology and physiology of this species is relatively unknown, and pollinating mechanisms, vegetative regeneration and any special requirements for germination are not known (WA CALM 2006). This species has shown regrowth following wildfire and may germinate following fire.

It is advisable to conduct surveys, especially opportunistic surveys, for the Gibson Wattle during the flowering season (August–September). Surveys at other times of the year should focus on known populations in areas of similar soil and vegetation types (WA CALM 2006).

The Gibson Wattle has been confused with Acacia kochii which has larger phyllodes, arranged in bundles in association with a thorn, longer flower heads and peduncles and longer pods which are not tightly coiled (Western Australian Herbarium 2006; WA CALM 2006).

Since 1997, the condition of the region where the Gibson Wattle occurs has degraded significantly with the biggest threats being feral animal and domestic stock grazing. Drought conditions can exacerbate threatening processes.

The threat from feral goats is considered to outweigh the threat from domestic stock. A survey conducted in 2002 revealed that feral goats had heavily grazed all known subpopulations. In 2001 and 2002, individual plants were recorded as being grazed back to 'spiny cushions', with upper branches defoliated (WA CALM 2006). After this grazing event subpopulation 6 had 80% dead (no plants have been found since) and subpopulation 1 had 5% dead (subsequently, a substantial population increase was observed). Proportion of mortality was not recorded for other populations. In the early 2000s a Landcare teacher counted 4000 feral goats in the region occupied by the Gibson Wattle (WA CALM 2006).

In late October 2002 subpopulation 2, on Mount Singleton at Mount Gibson Station, was within an area burnt by wildfire (WA CALM 2006). The effect of this event on the subpopulation is unknown. The nearby subpopulation 6 was not burnt during this event.

Minister's reason for Recovery Plan decision

The Gibson Wattle is known from six subpopulations with a low number of mature individuals. The species does not occur in any formal conservation reserves and most of the known localities are not being managed for conservation purposes. The species is subject to significant ongoing threats which can be better managed with a recovery plan in place (TSSC 2008aeg).

Recovery actions

Management actions for this species are described by Patrick (2001) and the Threatened Species Scientific Committee (TSSC 2008aeb). These actions include:

  • Raise awareness of flora and liaise with pastoralists, officers from the Western Australian Department of Agriculture and the Central Agricultural and Pastoral Aboriginal Corporation.
  • Resolve over-stocking land degradation problems.
  • Investigate and implement fencing options.
  • Develop and implement a management plan for the control and eradication of feral goats.
  • Determine the Gibson Wattle's response to wildfire and implement a suitable fire management strategy.
  • Conduct further surveys and monitor threatened flora on Mount Singleton.
  • Monitor effectiveness of management actions.
  • Investigate formal conservation arrangements or further management agreements.

The Pastoral Lands Board of Western Australia and the Western Australia Soil and Land Conservation Council (in recess) took steps to improve management of stations that may support the Gibson Wattle. Efforts have been made to improve pastoralist awareness, improve stock distribution and remove grazing pressure from degraded areas. Mount Gibson Station has begun destocking to reduce grazing pressure of stock in the future. The progress of this program is uncertain and the threat from feral goats is considered a greater threat than feral stock (WA CALM 2006). At Mount Gibson Station, where destocking has occured and goats removed, new plant growth has been recorded (TSSC 2008aeg). Despite efforts, feral goat numbers are not being consistently reduced across all sites and detrimental impacts from goats are likely to persist into the future (TSSC 2008aeg).

Management actions for this species are described in the Declared Rare and Poorly Known Flora in the Geraldton District (Patrick 2001) and the Commonwealth Conservation Advice on Acacia imitans (TSSC 2008aeb). The Competition and land degradation by unmanaged goats (DEWHA 2008ada) may assist in the mitigation of the feral goat threat.

The following table lists known and perceived threats to this species. Threats are based on the International Union for Conservation of Nature and Natural Resources (IUCN) threat classification version 1.1.

Threat Class Threatening Species References
Agriculture and Aquaculture:Livestock Farming and Grazing:Grazing pressures and associated habitat changes Commonwealth Conservation Advice on Acacia imitans (Threatened Species Scientific Committee (TSSC), 2008aeb) [Conservation Advice].
Commonwealth Listing Advice on Acacia imitans (Threatened Species Scientific Committee (TSSC), 2008aeg) [Listing Advice].
Climate Change and Severe Weather:Droughts:Drought Acacia imitans Interim Recovery Plan 2009-2014 (Department of Environment and Conservation, 2010a) [Recovery Plan].
Ecosystem/Community Stresses:Indirect Ecosystem Effects:Restricted geographical distribution (area of occupancy and extent of occurrence) Commonwealth Conservation Advice on Acacia imitans (Threatened Species Scientific Committee (TSSC), 2008aeb) [Conservation Advice].
Energy Production and Mining:Mining and Quarrying:Habitat damage caused by exploration drilling Acacia imitans Interim Recovery Plan 2009-2014 (Department of Environment and Conservation, 2010a) [Recovery Plan].
Human Intrusions and Disturbance:Human Intrusions and Disturbance:Human induced disturbance due to unspecified activities Acacia imitans Interim Recovery Plan 2009-2014 (Department of Environment and Conservation, 2010a) [Recovery Plan].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Grazing, tramping, competition and/or habitat degradation Capra hircus (Goat) Acacia imitans Interim Recovery Plan 2009-2014 (Department of Environment and Conservation, 2010a) [Recovery Plan].
Commonwealth Conservation Advice on Acacia imitans (Threatened Species Scientific Committee (TSSC), 2008aeb) [Conservation Advice].
Commonwealth Listing Advice on Acacia imitans (Threatened Species Scientific Committee (TSSC), 2008aeg) [Listing Advice].
Natural System Modifications:Fire and Fire Suppression:Inappropriate prescribed regimes and/or vegetation management to control fire regimes Acacia imitans Interim Recovery Plan 2009-2014 (Department of Environment and Conservation, 2010a) [Recovery Plan].
Protected status:Protected status:Lack of secure conservation land tenure Commonwealth Listing Advice on Acacia imitans (Threatened Species Scientific Committee (TSSC), 2008aeg) [Listing Advice].
Species Stresses:Indirect Species Effects:Low genetic diversity and genetic inbreeding Acacia imitans Interim Recovery Plan 2009-2014 (Department of Environment and Conservation, 2010a) [Recovery Plan].
Species Stresses:Indirect Species Effects:Low numbers of individuals Acacia imitans Interim Recovery Plan 2009-2014 (Department of Environment and Conservation, 2010a) [Recovery Plan].

Department of Environment and Conservation (2010a). Acacia imitans Interim Recovery Plan 2009-2014. [Online]. Kensington, Western Australia: Department of Environment and Conservation. Available from: http://www.environment.gov.au/biodiversity/threatened/publications/recovery/acacia-imitans.html.

Department of the Environment, Water, Heritage and the Arts (DEWHA) (2008ada). Competition and land degradation by unmanaged goats. [Online]. Canberra: DEWHA. Available from: http://www.environment.gov.au/biodiversity/threatened/publications/tap/goats08.html.

Maslin, B.R. (1999). Acacia miscellany 16. The taxonomy of fifty-five species of Acacia, primarily Western Australia, in section Phyllodineae (Leguminosae: Mimosoideae). Nuytsia. 12(3):311-411.

Patrick, S.J. (2001). Declared Rare or Poorly Known Flora in the Geraldton District. [Online]. Wildlife Management Program No 26. Perth, Western Australia: Department of Conservation and Land Management. Available from: http://www.dpaw.wa.gov.au/plants-and-animals/threatened-species-and-communities/threatened-plants.

Threatened Species Scientific Committee (TSSC) (2008aeb). Commonwealth Conservation Advice on Acacia imitans. [Online]. Department of the Environment, Water, Heritage and the Arts. Available from: http://www.environment.gov.au/biodiversity/threatened/species/pubs/65211-conservation-advice.pdf.

Threatened Species Scientific Committee (TSSC) (2008aeg). Commonwealth Listing Advice on Acacia imitans. [Online]. Department of the Environment, Water, Heritage and the Arts. Available from: http://www.environment.gov.au/biodiversity/threatened/species/pubs/65211-listing-advice.pdf.

Western Australia Department of Conservation and Land Management (WA CALM) (2006). Records held in CALM's Declared Flora Database and rare flora files. Perth, Western Australia: WA CALM.

Western Australian Herbarium (2006). Florabase - The Western Australian Flora. [Online]. Perth, Western Australia: Department of Conservation and Land Management. Available from: http://florabase.calm.wa.gov.au/.

EPBC Act email updates can be received via the Communities for Communities newsletter and the EPBC Act newsletter.

This database is designed to provide statutory, biological and ecological information on species and ecological communities, migratory species, marine species, and species and species products subject to international trade and commercial use protected under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act). It has been compiled from a range of sources including listing advice, recovery plans, published literature and individual experts. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. Individuals and organisations should consider all the available information, including that available from other sources, in deciding whether there is a need to make a referral or apply for a permit or exemption under the EPBC Act.

Citation: Department of the Environment (2014). Acacia imitans in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Sun, 13 Jul 2014 02:53:01 +1000.