Thelymitra atronitida (an orchid) - critically endangered species listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the orchid Thelymitra atronitida Jeanes 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.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Thelymitra atronitida Jeanes (Black-hooded Sun Orchid) (family Orchidaceae) is a terrestrial orchid, with a solitary basal linear to linear-lanceolate leaf 15-35 cm long and 5-12 mm wide, and a single flowering stem 30-50 cm tall. Flowers are 2-8 (rarely to 16) in number, each 14-26 mm diam., dark blue with darker longitudinal veins. The column has tufts of white hairs. The anthers are hooded by a post-anther lobe that is distinctly glossy black in colour with a yellow apex. The species is facultatively autogamous. Flowering has been recorded in New South Wales from August to December. Full descriptions and comments on distinctions from similar species are available in Jeanes (2000, including illustrations), Jeanes (2004), and Jones (2006).

2. In New South Wales, Thelymitra atronitida is known from two highly disjunct localities, Cape Solander in Botany Bay National Park in southern Sydney, and Bago State Forest south of Tumut. The known occurrences in this state fall in parts of the Sutherland and either or both of the Tumut and Tumbarumba Local Government Areas. The species also occurs in coastal and low-montane regions of eastern Victoria.

3. Thelymitra atronitida at Cape Solander is recorded from shallow black peaty soil in coastal heath on sandstone. In the Bago area it is recorded as occurring in open forest with a heathy understorey on well-drained sand or clay-loam soils.

4. Both the Cape Solander and Bago State Forest populations fall within the circumscription of T. atronitida in the recent critical revision of the  T. pauciflora complex (Jeanes 2004). Jeanes however advises (pers. comm.) that while the Cape Solander (coastal) material is both morphologically and ecologically congruent with the mainly coastal Victorian populations (which include the Type of the species), there is a possibility that the ecologically different Bago population may on further research be found to be taxonomically distinct. On current data both Cape Solander and Bago State Forest populations satisfy the criteria for critically endangered irrespective of whether they are classified as separate taxa. This Determination is made on the basis of the populations being conspecific.

5. The size of the Cape Solander population is not known with certainty but data from the two collections to date note it as 'rare' and 'eight plants' (Jeanes pers. comm.). The Bago population of the species was estimated in 1999 as being close to 50 plants, but despite searches has not been seen at the site since logging activity in 2003/4 (P. Branwhite, in litt. 2005, J. Kelton  in. litt. 2006). These estimates indicate that the species has an extremely low number of mature individuals and that recently a very large reduction in population size has occurred.

6. Threats to this species are likely to include environmental and demographic stochasticity due to the small population sizes and disjunct distribution of populations. The most recent (2006) collection notes from the Cape Solander site indicate damage to the population from heavy rains affecting the skeletal soil. It is unclear whether there are any other extrinsic threatening processes at the Cape Solander site. Threatening processes specific to the Bago site are likely to include rooting by feral pigs, grazing and trampling by cattle and wild horses, forest harvesting operations, weed invasion, and possible illegal collection. 'Predation, habitat degradation, competition and disease transmission by Feral Pigs, Sus scrofa Linnaeus 1758' is listed as a Key Threatening Process under the NSW Threatened Species Conservation Act.

7. Thelymitra atronitida Jeanes 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 14

The species has undergone, is observed, estimated, inferred or reasonably suspected to have undergone or is likely to undergo within a time frame appropriate to the life cycle and habitat characteristics of the taxon:

(a) a very large reduction in population size,

based on

(d) an index of abundance appropriate to the taxon, and

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

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, and

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

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

(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 either:

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

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

and

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

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

Clause 17

The total number of mature individuals of the species is observed, estimated or inferred to be:

(a) extremely low.

Professor Lesley Hughes
Chairperson
Scientific Committee

Proposed Gazettal date: 09/11/07
Exhibition period: 09/11/07 - 18/01/08

References:

Jeanes JA (2000) Two new species of Thelymitra (Orchidaceae) from southeastern Australia.  Muelleria 14, 91- 97.

Jeanes JA (2004) A revision of the Thelymitra pauciflora R.Br. (Orchidaceae) complex in Australia.  Muelleria 19, 19-79.

Jones DL (2006) A complete guide to native orchids of Australia including the island territories. (Reed New Holland, Frenchs Forest NSW.)