Pterostylis saxicola (an orchid) - endangered species listing

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to listPterostylis saxicola D. L. Jones & M. A. Clem. (formerly known as Pterostylis sp E.), the Sydney Plains Greenhood orchid, as an ENDANGERED SPECIES on Part 1 of Schedule 1 of the Threatened Species Conservation Act.

The Scientific Committee has found that:

1.Pterostylis saxicola, the Sydney Plains Greenhood, is a ground orchid which was first collected in 1803. It was previously regarded as a form of Pterostylis gibbosa but is now recognised as a distinct taxon.

2.Pterostylis saxicola is described in the Flora of New South Wales (volume 4) under the name Pterostylis sp E. as:

Terrestrial herb. Rosette leaves 5-8, obovate, 1-2.5 cm long, 7-11 mm wide, margins entire. Scape to 25 cm high, with 2-4 closely sheathing stem leaves. Flowers 2-10, c.1.3 cm long, transparent with dark red-brown markings and suffusions, semi-erect. Dorsal sepal with an upcurved filiform point c. 3 mm long. Lateral sepals ovate in outline when flattened; joined part shallowly concave, margins strongly incurved, glabrous; free points filamentous, c. 5 mm long, curved forwards, divergent, 10 mm apart at the tips. Petals with a poorly developed proximal flange. Labellum broad-obovate, c. 5 mm long, c. 3 mm wide, dark red-brown, grooved; marginal trichomes 3-5 pairs, 2-3 mm long, white; basal lobe large, with 2 or 3 pairs of trichomes c. 0.7 mm long. Flowers Sept-Nov. Grows in shallow soil over sandstone sheets, often near streams; rare, from Picnic Point to Picton area.

3.Pterostylis saxicola is most commonly found growing in small pockets of shallow soil in depressions on sandstone rock shelves above cliff lines. The vegetation communities above the shelves where Pterostylis saxicola occurs are either shale/sandstone transitions or shale communities.

4.Pterostylis saxicola is known from only five current localities: Georges River National Park (near Yeramba Lagoon), Ingleburn, Holsworthy, Peter Meadows Creek and St Marys Towers near Douglas Park.

5. The total known population is approximately 500 individuals, and individual populations are small. Only the Georges River National Park population is within a conservation reserve; up to 40 individual plants have been recorded in this population, but in 1996 only a few plants were found.

6. The largest known population occupies an area of only 20 x 15 metres. The localised habitat requirements mean that entire populations could be eliminated by events such as track creation, treefall or a single inappropriate fire. Part of one population has been destroyed by a track created by horse riders.

7. Developmental pressures, and increased access and use of sites, are likely to result in habitat loss and degradation, directly threatening existing populations and reducing the area of available habitat.

8. In view of 5, 6 and 7 above the Scientific Committee is of the opinion that Pterostylis saxicola is likely to become extinct in nature in NSW unless the circumstances and factors threatening its survival or evolutionary development cease to operate.

Associate Professor Paul Adam

Deputy Chairperson

Scientific Committee

Gazetted: 31/10/97

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Page last updated: 28 February 2011