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National recovery plan for Arachnorchis woolcockiorum (syn. Caladenia woolcockiorum) (Woolcock's spider orchid)

Doug Bickerton
National Parks and Wildlife SA
In partnership with Threatened Plant Action Group, February 2003

Note: This publication has been superseded by the Recovery Plan for Twelve Threatened Orchids in the Lofty Block Region of South Australia 2010

Recovery Plan for Arachnorchis woolcockiorum cover page

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Part A: Information Components

Background Information

The Lofty Block Threatened Orchid Recovery Project is a partnership managed jointly by South Australia‘s Department for Environment and Heritage and the community group Threatened Plant Action Group. The Natural Heritage Trust has provided funding to write and implement Recovery Plans for 12 threatened orchid taxa found in South Australia, including Arachnorchis woolcockiorum.

Taxonomy

In 2001 the orchid genus Caladenia underwent taxonomic review and subsequently Jones et al (2001) proposed a reclassification of the genus that entails the inclusion of Caladenia woolcockiorum in a new genus titled Arachnorchis. In February 2003 the Adelaide Plant Biodiversity Centre officially adopted the name change. As a consequence, this document will refer to the species as Arachnorchis woolcockiorum, except when referring to field specimen collections and older documents that use the previous nomenclature Caladenia woolcockiorum.

The Role of Indigenous People and their Knowledge

Indigenous communities involved in the regions affected by this plan have not yet been identified.  However this plan has been referred to the Aboriginal Partnerships Section of DEH, who will undertake consultation with the relevant indigenous communities.  The consultation will determine the role and interests of indigenous communities with regard to the implementation of this plan.

Social and Economic Impacts

It is not anticipated that any adverse impacts will eventuate as a result of the implementation of this plan. The extant sub-populations are all found in Mount Remarkable National Park and the only suitable areas of critical habitat are either in Conservation Parks or in remnant vegetation managed by Forestry SA. It is unlikely that the implementation of this recovery plan would create an adverse economic impact, since clearance of vegetation for land development at these sites without prior permission would contravene South Australia‘s Native Vegetation Act (1991).

International Obligations

Although Caladenia (syn. Arachnorchis) woolcockiorum is listed under CITES, this recovery plan does not affect Australia‘s obligations under international agreements.

Current Species Status

Arachnorchis woolcockiorum (Woolcock‘s spider orchid) is listed as nationally Vulnerable under the Commonwealth‘s Environment Protection and Biodiversity Conservation (EPBCEPBC) Act (1999). Briggs & Leigh (1995) listed the orchid as 2VC-, because its geographic range is less than 100 km2, all known populations are within a national park, and the reserved population size was not accurately known. Since the species was first described (Jones, 1991) its conservation status has not changed. According to the IUCN criterion VU D2 (IUCN, 1994) the species is Vulnerable because the known total area of occupancy (32ha) is considerably less than 100 km2. The extent of occurrence of A. woolcockiorum is mostly limited to a region of difficult access, and as such there is insufficient historical data on population size and fluctuations. For this reason the species cannot be seen to conform to any IUCN criteria for listing as an Endangered species, however it is predominantly contained within a 12km2 area, and an inappropriate disturbance such as disease, weed invasion, unsuitable fire regime or grazing pressure could quickly force its status to Endangered or worse.

Distribution and Population Size

In 2002 it was estimated that 3500 – 4500 plants were in existence at 15 locations (see Appendices). These locations were thought to comprise four subpopulations including in total 1500 flowering plants and 2000 – 3000 juveniles and non-flowering mature plants. The annual flowering rate of a subpopulation of spider orchids may vary considerably depending on seasonal conditions, and mature plants do not necessarily flower in consecutive years.

The known distribution is predominantly in an area measuring 2km x 6km in the centre of the Park, although scattered individuals can also be seen in the Park 1.5 – 3km west of the main subpopulations (see Figure 1). Historical records of A. woolcockiorum near Mt Remarkable summit and near Mambray Creek are listed on the Threatened Plant Population Database (TPPD), however the species was not seen at these sites in 1999 despite concerted searches in difficult terrain.

Region Covered by the Plan

The species is endemic to South Australia, where it is confined to Mount Remarkable National Park (MRNP) in the Southern Flinders Ranges (Figure 1). The Plan will focus primarily on MRNP, but will include other areas of similar habitat in the Southern Flinders Ranges and Northern Lofty Ranges.

Since 1998, Project Officers have conducted extensive searches to locate subpopulations of A. woolcockiorum and have begun accumulating data on critical habitat, population size, distribution and threatening processes. Consequently, NPWSA staff members are being consulted with regards to appropriate management at and near known locations, particularly track maintenance and fire prevention procedures.

Biodiversity benefits

As is typical of many native orchids, A. woolcockiorum is an indicator of a healthy open woodland or open forest community, because spider orchids are usually found where there is a lack of weeds, an available supply of food for pollinators and not too many vertebrates. Hence, appropriate management of A. woolcockiorum sites will also improve the viability and quality of the native vegetation in general. Continued monitoring of A. woolcockiorum will also assist in the understanding of other closely related species of the Arachnorchis patersonii complex, including the nationally endangered A. argocalla and A. behrii.

Relationship to Other Documents

The Recovery Plan assisted in the fine-tuning of the MRNP Management Plan (Croft, 2000). It will also aid in the future drafting of a Fire Management Policy for MRNP. Additionally, the draft Regional Biodiversity Plan for the Northern Agricultural Districts (Graham et al, 2001) lists Caladenia woolcockiorum as a priority species, and the actions recommended therein are complementary to those recommended in this Recovery Plan.

Recovery Team

The Lofty Block North Threatened Orchid Recovery Team manages the recovery of A. woolcockiorum. The Team includes the Senior Ecologist and Ecologist, Threatened Species Unit (NPWSA); Regional Ecologist for Northern Agricultural District (NPWSA); District Ranger, Mambray Creek Office (NPWSA) and members from the Threatened Plant Action Group (TPAG) and the Native Orchid Society of South Australia (NOSSA).