Genoplesium plumosum - critically endangered species listing

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the terrestrial orchid, Genoplesium plumosum (Rupp) D.L.Jones & M.A.Clem. (Tallong Midge Orchid) as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act, and as a consequence, to omit reference to Genoplesium plumosum (Rupp) D.L.Jones & M.A.Clem. from Part 1 of Schedule 1 (Endangered species) of the Act. Listing of critically endangered species is provided for by Part 2 of the Act.

 

The Scientific Committee has found that:

 

1. Genoplesium plumosum (Rupp) D.L.Jones & M.A.Clem. (family Orchidaceae) is a terrestrial herb of the Midge Orchid genus. It was described by Jones (2006), under the nomenclatural synonym Corunastylis plumosa, as follows: “Leaf 100-200 mm long; free part 15-30 mm long, ending below flowers. Spike 10-30 mm tall, 1-8 flowered. Flowers moderately crowded, semi-nodding, 8 x 5 mm, greenish with purple stripes and reddish purple labellum. Dorsal sepal 7 x 3 mm; margins hairless; apex sharply pointed. Lateral sepals divergent, 9 x 1 mm; apex pointed. Petals 6.5 x 1.5 mm; margins hairless; apex sharply pointed. Labellum stiffly hinged, oblong, 5.5 x 2 mm, moderately thick and fleshy; margins sparsely hairy; apex pointed, recurved. Callus extending nearly to labellum apex.”

 

2. Genoplesium plumosum was first described by Herman Rupp in 1942 as Prasophyllum plumosum. The name was changed to Genoplesium plumosum by Jones & Clements (1989), and again by Jones et al. (2002) to Corunastylis plumosa when transferring most species of Genoplesium into Corunastylis. This recent taxonomic change has not been widely accepted, however, and the name Genoplesium plumosum is still the most widely used in NSW.

 

3. Genoplesium plumosum is endemic to New South Wales. The original collection of Genoplesium plumosum was from Kurnell in southern Sydney but the species has not been observed there for over 80 years. The only currently known populations are in the Tallong-Wingello district on the edge of the Southern and Central Tablelands (Copeland 2008). Several small colonies are known within and close to the village of Tallong. A second population has recently been recorded to the south-east of Wingello in Morton National Park, the only known occurrence within a conservation reserve.

 

4. Genoplesium plumosum grows in skeletal soils on flat to gently sloping sheets of sandstone. The vegetation is usually a low heath dominated by Kunzea parvifolia, Calytrix tetragona and a number of smaller herbaceous species. Like all midge orchids, the above-ground parts of Genoplesiumplumosum die back after fruiting and the species exists as an underground tuber for most of the year. The flowering period varies from year to year but usually occurs 4-6 weeks after good summer/autumn rains. As for most Australian terrestrial orchids, the species is believed to be semi- or fully-dependent on a mycorrhizal symbiont.

 

5. Genoplesium plumosum has a very highly restricted geographic distribution. Its current area of occupancy is estimated to be approximately 20 km2 (Copeland 2008), based on the number of occupied 2 x 2 km grids, the spatial scale for assessment recommended by IUCN (2008). Its extent of occurrence is also estimated to be approximately 20 km2. Both of these estimates exclude the former population at Kurnell which has not been rediscovered despite extensive searches of suitable habitat in the area (Bishop 2000; NSW NPWS 2002).

 

6. The total known population of Genoplesium plumosum is estimated to comprise 250-280 mature individuals (Copeland 2008). Only 12 flowering plants were recorded within Morton National Park during the last survey in 2001. The original population may have been considerably larger, however, due to the likely loss of numerous plants and populations as a result of clearing of suitable habitat. Further clearing of habitat for residential blocks in the Tallong district is a continuing threat. Grazing by various herbivores (e.g. rabbits and wallabies) is also considered to be a major threat to the few remaining individuals (NSW NPWS 2002). ‘Clearing of native vegetation’ and ‘Competition and grazing by the feral European Rabbit Oryctolagus cuniculus (L.)’ are listed as Key Threatening Processes under the Threatened Species Conservation Act 1995.

 

7. Genoplesium plumosum (Rupp) D.L.Jones & M.A.Clem. is eligible to be listed as a Critically Endangered species as, in the opinion of the Scientific Committee, it is facing an extremely high risk of extinction in New South Wales in the immediate future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:

 

Clause 15

The geographic distribution of the species is estimated or inferred to be:

(a) very highly restricted,

and

(d) a projected or continuing decline is observed, estimated or inferred in:

(i) an index of abundance appropriate to the taxon,

(ii) geographic distribution, habitat quality or diversity, or genetic diversity; and

(e) the following conditions apply:

(i) the population or habitat is observed or inferred to be severely fragmented;

(ii) all or nearly all mature individuals are observed or inferred to occur within a small number of populations or locations.

 

 

Professor Lesley Hughes

Chairperson

Scientific Committee

 

 

Proposed Gazettal date: 21/11/08

Exhibition period: 21/11/08 – 23/01/09

 

References

Bishop T (2000) ‘Field guide to the orchids of New South Wales and Victoria. 2nd edition’. (University of New South Wales Press: Sydney)

Copeland LM (2008) ‘Conservation status of Genoplesium plumosum (Rupp) D.L.Jones & M.A.Clem. (Orchidaceae) in New South Wales.’ Report to the NSW Scientific Committee, Sydney.

IUCN (2008) ‘Guidelines for using the IUCN Red List Categories and Criteria. Version 7.0.’ (Standards and Petitions Working Group of the IUCN Species Survival Commission Biodiversity Assessments Sub-committee: Switzerland)

Jones DL (2006) ‘A complete guide to native orchids of Australia including the Island Territories’. (Reed New Holland: Sydney)

Jones DL, Clements MA (1989) Reinterpretation of the genus Genoplesium R.Br.(Orchidaceae: Prasophyllinae).  Lindleyana 4(3): 139-145.

Jones DL, Clements MA, Sharma IK, Mackenzie AM, Molloy PJ (2002) Nomenclatural notes arising from studies into the Tribe Diurideae (Orchidaceae). The Orchadian 13(10): 437-468.

NSW National Parks and Wildlife Service (2002) ‘Approved recovery plan for the Tallong Midge Orchid (Genoplesium plumosum)’. (NSW National Parks and Wildlife Service: Hurstville, NSW)

Page last updated: 28 February 2011