Zieria formosa - critically endangered species listing
The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the shrub Zieria formosa J.D. Briggs & J.A. Armstr. as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act, and as a consequence, omit reference to Zieria formosa J.D. Briggs & J.A. Armstrong from Part 1 of Schedule 1 (Endangered species). 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. Zieria formosa J.D. Briggs & J.A. Armstr. (family Rutaceae) has been described by Armstrong (2002) as:
“Rounded shrub up to 1.5 m high and 1 m across; younger branches terete, tuberculate, with a dense pubescence of short stellate hairs (also covering the tubercles); older branches less tuberculate, glabrescent. Leaves palmately trifoliolate, opposite, petiolate. Petiole 2.4 mm long, tuberculate, with a dense pubescence of short stellate hairs. Central leaflet lanceolate (10) 15-30 (37) x (2) 3-5 (6) mm, light green above, slightly lighter again below; upper surface tuberculate, densely pubescent with short stellate hairs, primary vein deeply sunken, secondary veins also sunken; lower surface sparsely tuberculate, with a dense velvety indumentum of short stellate hairs; apex obtuse (occasionally almost acute); margin slightly dentate, strongly recurved; primary vein prominently raised, tuberculate and densely stellate-pubescent; secondary veins slightly raised. Secondary leaflets similar to the central leaflet but smaller, usually 0.75-0.85 times as long. Inflorescence axillary, slightly longer than the leaves (9) 26-45 (77)-flowered. Peduncle (3) 10-20 (24) mm long, tuberculate, densely stellate-pubescent. Primary bracts deciduous (only one bract or bracteole present at each node of the inflorescence), narrow oblanceolate, 1.5-6 x 0.5-1.5 mm, abaxial surface tuberculate, adaxial surface not tuberculate, both surfaces densely stellate-pubescent. Pedicel terete, 1-3 mm long, sparsely and inconspicuously tuberculate, densely stellate-pubescent. Flowers pale pink, occasionally fading almost white, very conspicuous, 6-9 mm diameter. Calyx lobes deltoid, 1.5-2 x 1-1.2 mm at their base, very much shorter than the petals and about twice the length of the calyx tube, tuberculate and densely stellate-pubescent on the abaxial surface, not tuberculate and sparsely hairy on the adaxial surface with appressed mostly simple hairs, the surface distinctly reddish-brown in fresh and dried specimens and the apex terminated with a red tubercle. Petals valvate in bud, obovate-elliptic with an acute apex, 3.5-4 x 2 mm, with a small inflexed mucro at the apex; abaxial surface with sparsely scattered red-tinged tubercles and a fine pubescence of very short stellate hairs; adaxial surface glabrous-glabrescent, Stamens not persisting in the fruiting stage; filaments 1.5-1.8 mm long, glabrous, not tapering but with several conspicuous tubercles near their upper end and distinctly incurved from that point; anthers 0.7-0.8 x 0.6 mm, with a very small white apical point 0.15 mm long, versatile and attached at a point about one-third the distance from the base, the pollen is orange but this is normally hidden by the cream back to the inwardly and downwardly facing anthers (pollen cream in the dry state). Disc interrupted and distinct, glabrous, somewhat finely warty, pale pink infused with minute dark-blue dots. Ovary glabrous, densely tuberculate, red-brown in colour. Style 1-1.2 mm long, glabrous. Stigma 0.3-0.4 mm broad, lobed. Fruit dark red-brown when immature, often becoming greenish-brown at maturity, densely tuberculate (i.e. glands obvious on carpel surface), glabrous or occasionally with very sparsely scattered stellate hairs. Cocci lacking an appendage. Seed dark brown to grey-brown often with a few black patches, striate, (1.5) 2-2.5 (2.8) x (I) 1.2-1.6 (1.8) mm; the covering to the raphe smooth and shiny, not striate. Seed surface: ridges well-developed, flattened and long; branches and cross-ridges occasional. Elaisosome 1.5-2.5 x 0.8-1.1 mm.”
2. Zieria formosa was first discovered in 1986. The species has been known by a number of informal names, including ‘ Z. formosa (Armstrong 5090) ms’ (Armstrong & Harden 2002), ‘ Z. sp. H’ (Armstrong 1991), ‘ Z. sp. 7’ (Briggs & Leigh 1988) and ‘ Z. sp. O (Lochiel)’ (J.D. Briggs pers. comm. 2008). Zieria formosa is closely related to Z. buxijugum, from which it is distinguished by the presence of small terminal appendages on its anthers and narrower leaflets (2-3 mm wide cf. 3-5 mm wide).
3. Zieria formosa is endemic to New South Wales and is restricted to a single population on private land south-west of Pambula. The species is not known to occur in any conservation reserves and further surveys in and around the area have failed to locate any additional populations (Briggs & Leigh 1990; Armstrong 2002, J.D. Briggs pers. comm. 2008).
4. Zieria formosa grows in skeletal, grey, sandy loam amid broken rocks and boulders (Briggs & Leigh 1990). The species produces masses of pale pink flowers from September to October, and most seed-shed takes place by late December (Briggs & Leigh 1990; Armstrong 2002; NSW NPWS 2002). The fire response of this species is unknown, however many species of Zieria are killed by fire.
5. In 1987, 125 mature individuals were present at the site (Briggs & Leigh 1990). At the time of the most recent census in 2002, the population had declined to approximately 40 mature individuals, apparently as a consequence of severe drought conditions experienced during 1997-1998 (Armstrong 2002; NSW NPWS 2002; J.D. Briggs pers. comm. 2008). The extent of occurrence and area of occupancy are each estimated at 4 km2, based on 2 x 2 km grid squares, the scale recommended for assessing areas of occupancy by IUCN (2008).
6. Zieria formosa is threatened by demographic and environmental stochasticity due to its very highly restricted distribution and extremely low numbers of mature plants. The population appears to be particularly susceptible to extended dry spells, which may be compounded by wildfires. Increasing frequency and intensity of drought in the future (Hennessy et al. 2004) may further threaten the species. Habitat degradation and weed infestation due to subdivision of the surrounding land for rural residential development may pose an additional threat (NSW NPWS 2002). It may be inferred from these threats that the species is undergoing a continuing decline in abundance, and in habitat area and quality. ‘Anthropogenic Climate Change’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.
7. Zieria formosa J.D. Briggs & J.A. Armstr. 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
Clause 16The 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
Clause 17
The total number of mature individuals of the species is observed, estimated or inferred to be:
(a) extremely low.
Dr Richard Major
Chairperson
Scientific Committee
Proposed Gazettal date: 31/07/09
Exhibition period: 31/07/09 - 25/09/09
The NSW Threatened Species Scientific Committee undertook a review of this species in 2022 and found that the threat status is unchanged. The Conservation assessment report may be downloaded: Conservation assessment report Ziera formosa (PDF 263KB).
References:
Armstrong JA (1991) Zieria. In ‘Flora of New South Wales. Volume 2’. (Ed. GJ Harden). (University of New South Wales Press: Kensington).
Armstrong JA (2002) Zieria (Rutaceae): a systematic and evolutionary study. Australian Systematic Botany 15, 277-463.
Armstrong JA, Harden GJ (2002) Zieria. In ‘Flora of New South Wales. Volume 2’. (Ed. GJ Harden). (University of New South Wales Press: Kensington).
Briggs JD, Leigh JH (1988) ‘Rare or threatened plants’: 1988 revised edition. Australian National Parks and Wildlife Service Special Publication No. 14, Canberra.
Briggs JD, Leigh JH (1990) Delineation of Important Habitats of Threatened Plant Species in South-Eastern New South Wales. Australian Heritage Commission, Canberra.
Hennessy K, McInnes K, Abbs D, Jones R, Bathols J, Suppiah R, Ricketts J, Rafter T, Collins D, Jones D (2004) 'Climate change in New South Wales. Part 2: Projected change in climate extremes'. (CSIRO: Melbourne).
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)
NSW NPWS (2002) ‘Draft Recovery Plan for Zieria formosa, Zieria buxijugum and Zieria parrisiae’. NSW National Parks and Wildlife Service, Hurstville NSW.