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National recovery plan for Arachnorchis macroclavia (syn. Caladenia macroclavia) (Large - club 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Note: This publication has been superseded by the Recovery Plan for Twelve Threatened Orchids in the Lofty Block Region of South Australia 2010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 macroclavia 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 (TPAG). The Natural Heritage Trust (NHT) has provided funding to write and implement Recovery Plans for 12 threatened orchid taxa found in South Australia, including Arachnorchis macroclavia (Large-club Spider-orchid).


In 2001 the orchid genus Caladeniaunderwent taxonomic review and subsequently Jones et al (2001) published a proposal that green-comb spider-orchids in the Caladenia dilatata complex (such as C. macroclavia)be placed 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 macroclavia, except when referring to field specimen collections that were originally described as Caladenia macroclavia, and when referring to other documents that use the previous nomenclature.

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. Three of the extant sub-populations are found in reserves: Agery Reserve (under Heritage Agreement), Muloowurtie Conservation Reserve and Mona Rail Reserve. The other two confirmed extent sub-populations are on private property in remnant bushland, and 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).

Current Species Status

Arachnorchis macroclavia (Large-club spider-orchid) is listed as nationally Endangered under the Commonwealth's Environment Protection and Biodiversity Conservation Act (1999). Briggs & Leigh (1995) listed the orchid as Endangered, category 3ECi, because its geographic range is greater than 100 km2 and fewer than 1000 plants are found within conservation reserves. According to the IUCN criteria (IUCN, 2000) the species is Critically Endangered  (CR) because:

Distribution and Population Size

Arachnorchis(syn. Caladenia) macroclavia was previously thought to have a distribution that extended from Eyre Peninsula to the Murray Region, however it is currently considered that the species is endemic to South Australia's Yorke Peninsula. Three of Adelaide's Plant Biodiversity Centre (Adherb) collections from Eyre Peninsula (from Pt Lincoln in 1960, Stamford Hill in 1985 and Tumby Bay in 1942) were previously identified as Caladenia macroclavia. However it is thought the collections will now be re-classified by the Australian National Herbarium as Arachnorchis (syn. Caladenia) septuosa (Bates, pers. comm.). A specimen from Karoonda in the Murray Region was identified by J.Z. Weber in 1992 as Caladenia macroclavia, but may also be reviewed (Bates, pers. comm.). The Threatened Plant Population Database (Dept. for Environment & Heritage, SA) records a sighting of a single Caladenia macroclavia in 1989 in Telowie Gorge CP (Northern Lofty Ranges), but the specimen was not collected and the species has not been seen at this site since the first sighting. All other sightings and collections of the species are from Yorke Peninsula (Figure 1).

To date there are five confirmed extant sub-populations of A. macroclavia (Agery Reserve, Mona Railway Reserve, Muloowurtie Conservation Reserve, Pt Julia site and Pt Vincent site). In 2002, only 43 of the spider-orchids found flowering at these sites were confirmed as A. macroclavia (see Table 1), and it is estimated that another 50 – 100 non-flowering plants exist. The largest subpopulation is at the Pt Vincent site, where 37 plants were in flower in 2002. All subpopulations of the species are small and in danger of extinction, but the Pt Vincent site is most important for the long-term survival of the species. The confirmed extent of occurrence is from the Pt Vincent site in the south to the Mona Railway Reserve in the north, and west to Agery Reserve (see Figure 1): an area of 240 km2.

There have been reports (Bates, pers.comm.) of a sixth sub-population in Stansbury Scrub (see Figure 1), however the site was extensively searched in 2002 and no A. macroclavia were found. NOSSA members (M. Houston, pers. comm.) have also reported sightings of A. macroclavia at two locations on Minlaton Road. Both sites were searched in August 2002 and some budding Arachnorchis sp. plants were staked, but these aborted or were grazed before identification was possible.

The Adelaide Plant Biodiversity Centre holds collections of Caladenia macroclavia from three other localities. Two of these are from sub-populations believed extinct (Nantawarra, 1978 and Warooka, 1953) and the third (near Ardrossan, 1880's) is possibly from the extant A. macroclavia sub-population at Muloowurtie Conservation Reserve.

Table 1: The number of Arachnorchis macroclavia sighted in flower at the monitoring sites in 2001 and 2002.
Site 2001 2002
Agery Reserve 7 uncertain
Mona Reserve 2 3
Muloowurtie Reserve 3 3
Pt. Julia property 1 uncertain
Pt. Vincent property 22 37
Total 35 43

Region Covered by the Plan

It is intended that the Plan will focus primarily on Yorke Peninsula in the Northern Agricultural District of South Australia, but this is dependent on taxonomic clarification of the specimens collected from other regions. If further sub-populations are found outside of Yorke Peninsula, similar management principles will apply.

Biodiversity benefits

Appropriate management of A. macroclavia sites will also improve the viability and quality of the native vegetation in general. Continued monitoring of A. macroclavia is likely to assist in the understanding of related species of the Arachnorchis dilatata complex, including the nationally endangered A. gladiolata.

Relationship to Other Documents

Recovery Team

The Lofty Block (North) Threatened Orchid Recovery Team manages the recovery of A. macroclavia. 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); members from TPAG and representatives of the Native Orchid Society of South Australia (NOSSA). The Nature Conservation Officer (National Trust, SA), as a member of the Lofty Block (South) Threatened Orchid Recovery Team, also provides input to the recovery of the species.