Prasophyllum uroglossum - critically endangered species listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the terrestrial orchid Prasophyllum uroglossum Rupp as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act, and as a consequence, to omit reference to Prasophyllum uroglossum Rupp 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.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Prasophyllum uroglossum Rupp (family Orchidaceae) is a terrestrial herb of the Leek Orchid genus described by Bishop (2000) as follows: “Leaf to 50 cm long, withered at flowering. Stem slender, to 30 cm, with up to 23 flowers. Flowers with a strong gardenia scent, 8 mm across, pale greenish brown to red-brown with pale margins to sepals and petals. Ovary swollen. Dorsal sepal ovate with tapered apex. Lateral sepals free or united at base, curving backwards, tips fleshy. Petals linear, acute. Labellum ovate with suddenly tapered narrow acute apex, bent back at 90 degrees above the middle, margins smooth; callus plate greenish, strongly raised and deeply channelled to form 2 wing-like ridges, ceasing just beyond the bend. Column appendages weakly S-shaped, remarkably long (3 mm) and reaching almost to bend in labellum.”

2. Prasophyllum uroglossum was first described by Herman Rupp in 1947 from the Burrawang district of New South Wales. The species was treated as a synonym of  Prasophyllum fuscum by Clements (1989) and Jones (2006), however, other taxonomists have maintained  Prasophyllum uroglossum as a distinct species (e.g. Bernhardt & Rowe 1993; Bishop 2000). Although the two species are similar,  P. uroglossum can be distinguished from  P. fuscum by its much longer midlobe on the labellum and by its callus which barely extends onto the midlobe.

3. Prasophyllum uroglossum is endemic to New South Wales where it is only known from Wingecarribee Swamp in the Burrawang district, south of Sydney. There are also unconfirmed reports of the species from Wildes Meadow, five kilometres to the south, and to the east near Robertson. These populations have not been recorded for many years, however, and there is some uncertainty surrounding their taxonomic status (Copeland 2008).

4. Prasophyllum uroglossum occurs along swamp margins in moist but not saturated peat to clay-peat soil at the ecotone between grassy woodland and swamp, and rarely extends into the swamp itself. It grows in open heathland where abundant light is available and where low shrubs such as  Leptospermum obovatum provide some shelter. Like many ground orchids,  Prasophyllum uroglossum has a dormant phase during summer and resprouts from an underground tuber in Autumn to form a short leaf. This leaf may develop further and the plants may flower from October to November. The response of the species to fire is unknown but enhanced flowering in the season following a fire is common within the genus  Prasophyllum (Bishop 2000; Jones 2006). Like most terrestrial orchids, the species is believed to be semi or fully dependent on a mycorrhizal symbiont.

5. Prasophyllum uroglossum is not known to occur in any conservation reserves.

6. Prasophyllum uroglossum has a very highly restricted geographic distribution. It is currently known from a single population and has an area of occupancy of no more than 8 km2 based on the species occupying two grids, each of 2 x 2 km, the spatial scale recommended for assessing areas of occupancy by IUCN (2008).

7. The total population of Prasophyllum uroglossum is currently estimated to include approximately 40-80 mature individuals. At least 100 mature individuals were estimated to be present in the early 1990’s (J. Briggs pers. comm., D. Jones pers. comm.). In a 2004 survey Briggs found only four plants although Briggs did not search all of the previously recorded patches. More recent and comprehensive surveys of the Wingecarribee Swamp population found 80 plants in 2005, 3 plants in 2006 and 31 plants in 2007 (S. Harrington, pers. comm.). The proportion of individuals in the population that emerge and flower therefore appears to vary considerably from year to year and may be influenced by environmental factors such as rainfall.

8. Prasophyllum uroglossum is currently threatened by invasion of exotic weed species including  Holcus lanatus (Yorkshire fog) and  Rubus fruticosus spp. agg (Blackberry). A major washout/collapse of Wingecarribee Swamp in 1998 has altered the hydrological conditions, resulting in apparent drying of soils at locations where  P.  uroglossum has been recorded. This increasing dryness has favoured the establishment of a number of weedy species that may otherwise have been excluded from the site. The species may also be susceptible to fragmentation of the woodlands and forests adjacent to the swamp and disturbance and fertiliser application associated with management of the adjacent pastures for livestock production. Fire regimes required for conservation of  Prasophyllum uroglossum are currently unknown.

9. Prasophyllum uroglossum Rupp 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 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;

(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.

Clause 16

The estimated total number of mature individuals of the species is:

(a) very low,

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;

(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.

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 18/12/09
Exhibition period: 18/12/09 – 05/03/10

References

Bernhardt P, Rowe RR (1993) Prasophyllum. In ‘Flora of New South Wales. Vol.4 ’. (Ed. GJ Harden) pp. 155-163 (University of New South Wales Press: Sydney)

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

Clements MA (1989) Catalogue of Australian Orchidaceae. Australian Orchid Research 1, 1-160.

Copeland LM (2008) ‘Clarification of the taxonomy, and a reassessment of the conservation status, of Prasophyllum fuscum,  P. uroglossum and  P. pallens (Orchidaceae) in NSW’ 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)