Gibson wattle (Acacia imitans) recovery plan




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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. Acacia imitans is not specifically listed under any international treaty and this plan does not affect Australia’s obligations under any other international agreements.



Indigenous consultation: A search of the Department of Indigenous Affairs Aboriginal Heritage Sites Register has identified that there are no sites of Aboriginal significance at or near populations of Acacia imitans. However, involvement of the Indigenous community has been sought through the Pindiddy Aboriginal Corporation (PAC) to determine whether there are any issues or interests identified in the plan. Recovery actions identified within this plan refer to continued liaison and cooperation with the managers of the land, and in the case of those populations which are located on Ninghan Station, this refers to the PAC.

Social and economic impact: The implementation of this recovery plan may have some social and economic impact as all populations of Acacia imitans occur on pastoral leases. Negotiations will continue with regard to the future management of these populations. Mt Gibson Station is managed for conservation so social and economic impacts on this pastoral lease are less likely.




Affected interests: All known populations are found on pastoral leases and protection of habitat may potentially impact on their management. Mining tenement holders may also be affected by actions referred to in this plan. Other affected interests include Telstra, Department of Aviation, Department of Industry and Resources and Department of Environment and Conservation.

Evaluation of the plan’s performance: DEC, in conjunction with the Geraldton District Threatened Flora Recovery Team (GDTFRT) will evaluate the performance of this plan. In addition to annual reporting on progress and evaluation against the criteria for success and failure, the plan will be reviewed following five years of implementation.



Recovery Plan objective: The objective of this plan is to abate identified threats and maintain or enhance viable in situ populations to ensure the long-term preservation of the species in the wild.

 

Recovery criteria


Criteria for success: The number of individuals within populations increase by ten percent or more and/or the number of populations increase over the term of the plan.

Criteria for failure: The number of individuals within populations decrease by ten percent or more and/or the number of populations decrease over the term of the plan.
Completed Recovery Actions


  1. The managers of the pastoral leases containing the populations of Acacia imitans have been notified and advised of the locations and their legislative responsibilities to protect the plants.

  2. The Geraldton District Flora Conservation Officer has liaised with managers.

  3. An area which included habitat of Acacia imitans was declared an Indigenous Protected Area in October 2006. Through this declaration, funds are being provided by the Department of Environment, Water, Heritage and the Arts to conduct a range of conservation initiatives. These included the erection of a goat proof fence which was completed in 2006.

  4. Mt Gibson Station, purchased by the Australian Wildlife Conservancy in 2001, has now largely been destocked.

  5. Sue Patrick, from DEC, conducted surveys for Acacia imitans over 11.5 days between April 1992 and April 2001. These surveys covered much of the species’ range, similar habitat close by, and hills west and north of known populations.

  6. Population 1 has been monitored since 1992. Population 2 was monitored in 1994 and 2004, and has not been located since. Populations 3, 4 and 5 have been monitored since 2001 and Population 6 was monitored from 2001 to 2004, but also has not been located since.

  7. The Threatened Flora Seed Centre (TFSC) holds five collections, totaling 5494 seeds, of Acacia imitans in storage at -18C. Of these, 323 seeds were collected from Population 3 and 2069 seeds collected from Population 5. In November 2004, an additional 323 seeds were collected from Population 3, 2741 seeds from Population 5 and 38 seeds from Population 6. Germination trials on seeds collected from Population 3 resulted in 97% germination, Population 5 - 92% germination and Population 3 - 100% germination. Other collections have not yet been tested. The germinants resulting from TFSC germination trials were given to the Botanic Gardens and Parks Authority (BGPA) nursery.

  8. Germination trials have been conducted, resulting in a 96.3% average germination rate.

  9. The Botanic Gardens and Parks Authority has two plants in its nursery.

  10. A nomination for listing under the Commonwealth Environment Protection and Biodiversity Conservation Act resulted in Acacia imitans being listed as Endangered in 2010.



Ongoing and future recovery actions





  1. Feral goat control is being implemented, with approximately 1,300 goats removed from Ninghan Station since the installation of a goat proof fence.

  2. Staff from DEC’s Geraldton District regularly monitor all populations.

  3. The GDTFT is overseeing the implementation of this plan.


Recovery actions


  1. Coordinate recovery actions

9. Conduct further surveys

  1. Liaise with relevant land managers and indigenous groups

10. Collect further seed

  1. Develop and implement a feral goat control strategy

11. Monitor the level of weeds impacting populations and undertake weed control if considered necessary

  1. Monitor populations

12. Start the translocation process, if necessary

  1. Resurvey Populations 2 and 6

13. Promote awareness

  1. Develop and implement a fire management strategy

14. Review the plan and need for further recovery actions

  1. Map habitat critical to the survival of Acacia imitans




  1. Obtain biological and ecological information




 

1. BACKGROUND

History
Collectively known as wattles, there are some 1000 species of Acacia found throughout Australia. One of the rarest is Acacia imitans which was first collected by Ken Newbey in 1965 and named by B.M. Maslin in 1999. Until formally named, the species was confused with Acacia kochii and the name imitans refers to it imitating that species.
During surveys by Conservation and Land Management (CALM) staff in April 1992 there was evidence that Acacia imitans was subject to grazing by goats that were common in the plants habitat at that time (S. Patrick1). In August 2000, large numbers of goats were recorded and, during surveys undertaken in 2001, individual plants of Acacia imitans were recorded as grazed back to “spiny cushions”, with phyllodes at the top of plants removed. Plant deaths were recorded in 2001 and 2002. The drought conditions experienced from 2001 to 2004 resulted in the grazing impact being particularly prominent over the plant’s habitat.
Following early rains in 2004, DEC staff recorded a significant increase in the number of mature plants at Population 1, commenting that many plants previously unrecognisable and dead-looking then had new growth.
The Australian Wildlife Conservancy purchased the pastoral lease for the Mt Gibson Station in 2001 and now manages the property for conservation.
In October 2006, the Pindiddy Aboriginal Corporation voluntarily declared two areas within Ninghan Station as Indigenous Protected Areas. The Ninghan Indigenous Protected Areas are currently managed in accordance with IUCN categories III and VI for conservation of biodiversity and associated cultural resources (DEWHA 2007b).

Description



Acacia imitans is a low, intricately branched and semi-prostrate shrub 0.3-1 m tall by 3m across. Branches divide into numerous short, ridged, smaller branchlets which end in a spine. Phyllodes are asymmetrical in shape, the upper margin straight or slightly concave, the lower margin convex, 3.5-7 mm long, 1.5-2.5 mm wide, thin, hairless and sharp-tipped. They are not grouped in clusters and are often bent backwards on the branches. Inflorescences are singular at each node, on a stalk 3-4 mm long. The flower head is golden, 6-8 mm long and 4-5 mm wide. Pods are tightly coiled to 7 mm long (when coiled) and 3 mm wide (Maslin 1999).
This species has been confused with Acacia kochii which occurs in the same area. Phyllodes of A. kochii are 1-2 cm long, grouped in bundles of 2-8 with a spine associated with each bundle. Flower heads are 7-13 mm long on stalks 1-2 cm. Pods are to 9 cm long and are not tightly coiled. A. erinacea also occurs in the same area and has a similar habit, small phyllodes and branches that form spines. It can be distinguished from A. imitans by its globular flower heads and pods which are short, straight and oblong, c. 8mm wide (Maslin 1999).

Distribution and habitat


Acacia imitans is currently known from 7 populations in a single area approximately 300 km northeast of Perth. Plants grow in disturbed, open locations on red loam amongst dolerite rocks on the summits and slopes of hills with Allocasuarina tessellata, A. dielsiana, Acacia acuminata, Grevillea species and Dodonaea inaequifolia. The extent of occurrence is estimated to be approximately 20 km2. There is insufficient data to calculate the area of occupancy, as not all populations have it recorded. There are currently approximately 661 plants known.
Summary of population land vesting, purpose and manager


Pop. No. & Location

DEC District

Shire

Vesting

Purpose

Manager

1. North East of Wubin

Geraldton

Yalgoo

Pastoral Lease

Pastoral

Pindiddy Aboriginal Corporation

2. North East of Wubin

Geraldton

Yalgoo

Pastoral Lease

Pastoral

Australian Wildlife Conservancy

3. North East of Wubin

Geraldton

Yalgoo

Pastoral Lease

Pastoral

Pindiddy Aboriginal Corporation

4. North East of Wubin

Geraldton

Yalgoo

Pastoral Lease

Pastoral

Pindiddy Aboriginal Corporation

5. North East of Wubin

Geraldton

Yalgoo

Pastoral Lease

Pastoral

Pindiddy Aboriginal Corporation

6. North East of Wubin

Geraldton

Yalgoo

Pastoral Lease

Pastoral

Australian Wildlife Conservancy

7. North East of Wubin

Geraldton

Yalgoo

Pastoral Lease

Pastoral

Australian Wildlife Conservancy



Biology and ecology
Acacia imitans is a member of the Mimosaceae family and is likely to have a similar biology and ecology to other members. Germination of Acacia imitans is likely to be triggered by natural disturbance events (physical or fire), which may explain why many plants are located in disturbed areas.
Galls were recorded on some plants in Population 6 during a survey in October 2003.
Germination trials conducted on seed collections made from Population 3 resulted in a 98.5% average success rate. Trials conducted on the 2001 seed collection made from Population 5 resulted in a 92% success rate (A. Crawford2 pers. comm.). Such a high success rate indicates there are other factors inhibiting natural recruitment, such as grazing of new seedlings, or insufficient germination triggers such as fire or other natural disturbance events.
Threats
Acacia imitans was declared as Rare Flora under the Western Australian Wildlife Conservation Act 1950 in April 2002 and is currently ranked as Critically Endangered (CR) against World Conservation Union (IUCN 2001) Red List criterion B1ab (iii) +2ab (iii) in Western Australia due to its extent of occurrence being less than 100 km2, its very small and restricted population sizes and its highly disturbed habitat which is continuing to decline in quality. Acacia imitans is listed as endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). Acacia imitans has a restricted distribution between Wubin and Paynes Find, where it is known from seven populations on pastoral leases. The main threats are grazing by feral goats, track maintenance, inappropriate fire regimes and drought.
Grazing by goats is a serious threat. Grazing removes new growth and reduces reproductive output. All populations have been seriously affected by grazing.
Track maintenance threatens most populations.
Inappropriate fire regimes may affect the viability of populations. As seeds of Acacia imitans are thought to germinate following fire, it is likely that occasional fires are needed for recruitment. A lack of fire may therefore result in population senescence and rapid decline.
Drought is a threat to all populations of Acacia imitans and has the potential to increase grazing impact as animals become more desperate for food.
Small population size increases the likelihood of populations being adversely impacted by a single stochastic event. As Acacia imitans populations are mostly very small, the likelihood of the species being adversely impacted by chance demographic or environmental event is increased. Small populations are also at a greater risk of loss of genetic diversity and inbreeding depression.
Mineral exploration is a potential threat to populations of Acacia imitans. All are located in areas covered by mining tenements.
The intent of this plan is to provide actions that will deal with immediate threats to Acacia imitans. Although climate change may have a long-term effect on the species, actions taken directly to prevent the impact of climate change are beyond the scope of this plan.
Summary of population information and threats

Pop. No. & Location


Year No. plants

Habitat condition

Threats

1. North East of Wubin

1992 ca. 100+

2004 ca. 200+

2007 ca. 200+

2009 ca. 200+



Moderate

Moderate


Moderate

Moderate


Grazing, drought, wildfire, small population size, mineral exploration, potential mining operations

2. North East of Wubin

1994 ca. 10+

2009 25


Healthy

Moderate


Grazing, drought, wildfire, small population size, mineral exploration, potential mining operations

3. North East of Wubin

2001 ca. 30

2004 ca. 30+

2006 33

2007 ca. 36+ (ca. 5+)



2009 30

Moderate

Poor


Moderate

Moderate


Moderate

Grazing, drought, wildfire, small population size, mineral exploration, potential mining operations

4. North East of Wubin

2001 30

2002 36


2007 ca. 300+

2009 300


Moderate

Poor


Moderate

Moderate


Grazing, drought, wildfire, small population size, mineral exploration, potential mining operations

5. North East of Wubin

2001 132

2006 ca. 80+

2007 ca. 100+

2009 100


Moderate

Moderate


Moderate

Moderate


Grazing, drought, wildfire, small population size, mineral exploration, potential mining operations

6. North East of Wubin

2001 ca. 6

2004 ca. 25+

2009 0


Poor

Healthy


None located

Grazing, drought, wildfire, small population size, mineral exploration, potential mining operations

7. North East of Wubin

2009 10

Poor


Grazing, drought, wildfire, small population size, mineral exploration, potential mining operations

( ) = number of seedlings. Population information obtained from DEC (2009)
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 Acacia imitans will require assessment. On-ground works should not be approved unless the proponents can demonstrate that they will not have a significant negative impact on the species, its habitat or potential habitat or on the local surface hydrology, such that drainage in the habitat of the species would be altered.
Habitat critical to the survival of the species, and important populations
Habitat critical to the survival of the species includes:

  • The area of occupancy of important populations.

  • Areas of similar habitat surrounding important populations (i.e. open areas in red loam amongst dolerite rocks - these provide potential habitat for natural range extension).

  • Remnant vegetation that surrounds and links populations (this is necessary to allow pollinators to move between populations).

  • The local catchment for the surface and ground waters that maintain the habitat of the species.

  • Additional occurrences of similar habitat that may contain the species or be suitable for future translocations.


Acacia imitans is listed as Critically Endangered in Western Australia and Endangered under the EPBC Act and it is therefore considered that all known habitat of wild populations is critical to the survival of the species and that all wild populations are important populations.
Benefits to other species or ecological communities
Recovery actions implemented for Acacia imitans will also improve the health of associated native vegetation. Additionally, two Critically Endangered and four Priority Flora occur in association with Acacia imitans. These taxa are listed in the table below.
Conservation-listed flora species occurring in habitat of Acacia imitans


Species Name

Conservation Status (Western Australia)

Conservation Status (EPBC Act 1999)

Acacia unguicula

Critically Endangered

Critically Endangered

Hybanthus cymulosus

Critically Endangered

Critically Endangered

Allocasuarina tessellata

Priority 1

-

Grevillea scabrida

Priority 3

-

Grevillea subtiliflora

Priority 1

-

Micromyrtus racemosa var. mucronata ms

Priority 1

-

For a description of the Priority categories see Atkins (2008).
Acacia imitans does not occur within a Threatened Ecological Community (TEC).

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