Pterostylis vernalis - 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 orchid Pterostylis vernalis (D.L. Jones) G.N. Backh. as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act. Listing of Critically Endangered species is provided for by Part 2 of the Act.

 

The Scientific Committee has found that:

 

1. Pterostylis vernalis (D.L. Jones) G.N. Backh. is the name currently accepted in NSW for this recently described species restricted to the Nowra area of the NSW south coast. The species was published as Speculantha vernalis D.L. Jones (Jones 2006). The species has also previously been known as Pterostylis sp. aff. parviflora (Spring) (Bishop 1996), and Pterostylis sp. aff. parviflora “Flatrock Creek”. Pterostylis vernalis (D.L. Jones) G.N. Backh. was listed under the name ‘Pterostylis sp. Flat Rock Creek (D.L.Jones 15873 & K.J.Fitzgerald) (Spring Tiny Greenhood)’ as a Critically Endangered species on the Environment Protection and Biodiversity Convservation Act 1999 in February 2010.

 

2. Pterostylis vernalis (D.L. Jones) G.N. Backh. is described by Jones (2006) under the name of Speculantha vernalis D.L. Jones as a ‘tuberous terrestrial herb. Plants 10-20 cm tall, not elongating in fruit. Rosettes 1-2, usually present at anthesis, terminating the parent tuber or on sterile plants. Rosette leaves 3-7 spreading; lamina ovate, 5-15 mm long, 4-10 mm wide, dark green; margins entire; apex acute, petioles slender, 3-12 mm long, narrowly winged, widening distally. Scape slender, wiry, 1-4-flowered. Sterile bracts 2-4, closely sheathing, ovate lanceolate, 6-10 mm long, 2-3 mm wide, acuminate. Floral bracts similar, sheathing the pedicel and ovary base. Pedicels 1-9 mm long, thin. Flowers moderately spaced, facing inwards, 1-3 open at once, 8-10 mm long, 4-4.5 mm wide, bulbous, green proximally with a prominent white patch towards the base of the galea, dark brown to blackish distally; galea slightly inflated at the base, erect before curving forwards in a semi-circle; dorsal sepal slightly longer than the petals, the distal parts of the dorsal sepal and petals strongly scabrous. Dorsal sepal ovate-lanceolate when flattened, 12-15 mm long, 6-9 mm wide, inflated at the base then tapered distally, boldly striped, acute to apiculate, dorsal surface scabrous. Lateral sepals erect, closely embracing the galea; sinus step-like at the top, the area bulbous when viewed from the side, shallowly notched medially when viewed from the front; frontal opening 3-3.5 mm wide; conjoined part 6.5-7.5 mm long, c 5-6 mm wide, narrowed to c. 2.5 mm across at the base, prominently striped; free points c. 3.5 mm long tapered, acuminate, curved forwards, the tips just reaching the top of the galea. Petals oblong 9-11 mm long, c. 3 mm wide, strongly falcate, white with brown stripes and markings, subacute; flange c. 1 mm across, broadly deltate, obtuse. Labellum erect, not visible through the sinus in any position, straight or slightly curved forwards near the apex, white with a brown medial stripe and brown margins. Labellum lamina elliptical to obovate, 3-4 mm long, 1.5-1.7 mm wide, obtuse to truncate; basal appendage decurved, c. 0.8 mm long, broadest at the base; apex erect, trifid. Callus a raised central reddish ridge c. 0.3 mm across. Column 4-5 mm long, curved away from the ovary at c. 60° at the base then erect, green and white. Column wings c. 1.3 mm long; basal lobe broadly deltate c. 0.5 mm long, white at an angle of c. 45°; apex broadly obtuse; inner margins adorned sparsely with short white cilia; mid-section c. 0.6 mm long, dark green; apical lobe narrowly linear, c. 0.7 mm long, acute. Anther c. 0.8 mm long, obtuse. Pollinia narrowly linear, c. 1.3 mm long, yellow, mealy. Stigma situated medially, broadly scutiform, c. 1.8 mm long, c. 1.5 mm wide, raised. Capsules erect, narrowly obovoid, 10-13 mm long, 4-5 mm wide, on pedicels to 10 mm long.’

 

3. Pterostylis vernalis is only known from the Nowra area on the NSW south coast. There are five known populations located to the west and south-west of Nowra. Four are within a few kilometres of each other, and one is located approximately 18 km to the south-west. The geographic distribution of Pterostylis vernalis is very highly restricted with the extent of occurrence less than 100 km2 based on a minimum convex polygon encompassing known locations, the recommended measure for extent of occurrence in the IUCN (2010) guidelines. The area of occupancy (AOO) is estimated to be 16-20 km² based on a 2 x 2 km grid the scale recommended by IUCN (2010). The actual on ground area of occupancy is likely to be less.

 

4. When Jones (2006) published Speculantha as a segregate of Pterostylis he noted that there were four species found in the vicinity of Nowra, however S. vernalis is the only species that flowers in spring (Jones 2006). S. vernalis was also distinguished from other species of Speculantha by the emergence of the rosettes before the development of the inflorescence. Further distinguishing features are given in Jones (2006).

 

5. Pterostylis vernalis is described by Jones (2006) as growing in open sites in shallow soil over sandstone sheets, in heath and heathy forest. The habitat for Pterostylis vernalis is quite specific, as it prefers the moisture regime associated with the flow of water through shallow soil over underlying rock.

 

6. The number of Pterostylis vernalis individuals is estimated to be low with approximately 450-500 known individuals. P. vernalis is a seasonal perennial, present above ground in the cooler months between late autumn to spring, and remaining as a dormant tuber underground over summer. Fluctuations in the plant numbers are unknown. The four northern populations may have once been considered as one population covering an area of approximately 3 km2. Urban development and infrastructure may have fragmented the population into the present patches. The location of the plants throughout this area may still be naturally patchy as they prefer areas near rock shelves. The rock shelf in the area is not constant, and the orchid prefers sections of thin soil over the rock shelf providing particular hydrological conditions.

 

7. Most known Pterostylis vernalis plants are located on land not reserved for conservation purposes. The exceptions are the southern-most population which is located in Jerrawangala National Park, and a part of one of the northern populations, which is located in Triplarina Nature Reserve. Both these populations are close to roads. The largest population, which contains over 50% of the known plants, is located on land that is likely to undergo development (Jones 2006).

 

8. Threats to the populations of Pterostylis vernalis include clearing of habitat, disturbance of habitat by vehicles and rubbish dumping, altered hydrological regimes, and illegal collection of the orchid (TSSC 2010). The largest site is potentially threatened by future planned urban development. The four northern-most populations are all in close proximity to infrastructure in the form of buildings, roads, or powerlines etc. Past clearing of habitat has most likely occurred in this area leading to a fragmentation of the population. The building of a main road has bisected one of the populations. Further development is proposed for this northern section of the distribution in the future (Jones 2006; TSSC 2010), which may lead to further habitat loss and fragmentation of the population and its habitat. ‘Clearing of native vegetation’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

 

9. Pterostylis vernalis (D.L. Jones) G.N. Backh. 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 2010:

 

Clause 7 restricted geographic distribution and other conditions

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 either of the following key indicators:

        

(a) an index of abundance appropriate to the taxon, or

(b) geographic distribution, habitat quality or diversity, or genetic diversity.

 

Dr Richard Major

Chairperson

Scientific Committee

 

Proposed Gazettal date: 08/07/11

Exhibition period: 08/07/11- 02/09/11

 

References:

 

Bishop T (1996) ‘Field Guide to the orchids of New South Wales and Victoria.’ (UNSW Press, Sydney)

 

IUCN Standards and Petitions Subcommittee. (2010). Guidelines for Using the IUCN Red List Categories and Criteria. Version 8.1. Prepared by the Standards and Petitions Subcommittee in March 2010. (http://intranet.iucn.org/webfiles/doc/SSC/RedList/RedListGuidelines.pdf.)

 

Jones DL (2006) Speculantha vernalis (Orchidaceae), A critically endangered new species from south-eastern New South Wales. The Orchadian 15 (6), 277-281.

 

Threatened Species Scientific Committee (TSSC) (2010). Commonwealth Listing Advice on Pterostylis sp. Flat Rock Creek (D.L.Jones 15873 & K.J.Fitzgerald) (Spring Tiny Greenhood). [Online]. Department of the Environment, Water, Heritage and the Arts. Canberra, ACT: Available from: (http://www.environment.gov.au/biodiversity/threatened/species/pubs/81967-listing-advice.pdf)

Page last updated: 08 July 2011