Zieria adenophora - proposed critically endangered species listing

NSW Scientific Committee - preliminary determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Preliminary Determination to support a proposal to list the shrub Zieria adenophora Blakely as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act, and as a consequence, to omit reference to Zieria adenophora Blakely 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.

The Scientific Committee has found that:

1. Zieria adenophora (family Rutaceae) is described by Armstrong (2002) as a ‘small, divaricate, densely tuberculate shrub up to 1 m. Younger branches not ridged, densely tuberculate, minutely pubescent (with simple hairs) all over; tubercles reddish-brown, glabrescent on top but pubescent at the base. Branches glabrescent, lenticellate. Leaves trifoliolate, opposite (very occasionally subopposite), petiolate. Petiole c. 1.5-2.0 mm long, tuberculate only on the abaxial surface, pubescent on both surfaces; tubercles glabrous. Central leaflet cuneate-obovate, c. 2.5-8.0 x 2.0-4.0 mm; upper surface prominently tuberculate, glabrous except for the occasional simple hair; lower surface tuberculate on the primary vein, glabrous except for the odd scattered hair, slightly more hirsute along the primary vein, the tubercles glabrous; apex rounded to emarginate; margin dentate (because of the large glandular tubercles) and slightly revolute; venation (excluding the primary vein on the lower surface) obscure on both surfaces. Inflorescence axillary, shorter than the leaves, c. 1-3-flowered. Peduncle c. 0.4-2.0 mm long, tuberculate, glabrescent. Bracts persistent, narrow obovate, c. 1.0-1.5 x 0.6-0.8 mm, foliaceous, glabrous, tuberculate on the abaxial surface only, otherwise similar to the lamina in all surface features but much smaller. Pedicel not ridged, c. 1.0-1.5 mm long, not tuberculate, pubescent. Flowers white or pale-pink, c. 5.0 mm diameter. Calyx lobes deltoid, c. 1.0 x 0.8 mm, very much shorter than the petals, tuberculate only on the abaxial surface, glabrous on both surfaces. Petals valvate in bud, c. 2.0-3.0 x 1.0 mm, with a small inflexed mucro at the apex, pubescent on the abaxial surface, glabrous to glabrescent adaxially, tubercles obvious on the abaxial surface towards the apex. Stamens not persisting in the fruiting stage; filaments c. l.0 mm long, glabrous to minutely hirsute, not prominently dilated towards the base, not warty towards the apex; anthers orbicular, c. 0.5 x 0.4 mm, not apiculate. Disc interrupted and distinct, glabrous. Ovary densely tuberculate, glabrous. Style c. 0.9 mm long, glabrous. Stigma c. 0.4 mm broad. Fruit tuberculate, glabrous. Cocci ovate, glabrous, lacking an appendage. Seed not seen’.

2. Zieria adenophora was first collected near Araluen in 1888 and described by (Blakely 1941). The species was not collected for another 100 years and was considered extinct (Briggs and Leigh 1990) until its rediscovery at Bells Creek in the Araluen Valley in the 1980s.

3. Zieria adenophora is endemic to New South Wales and known only from the Araluen area in the Southern Tablelands of NSW. This species occurs in shrubby vegetation growing in shallow sandy to gravelly loam, amongst granite boulders. Plants flower from August to October and are likely to be pollinated by insects.

4. Zieria adenophora has a very highly restricted geographic distribution. The species is known from only one locality within a total extent of occurrence and area of occupancy of less than 4 km2, based on 2 x 2 km grid cells, the scale recommended for assessment of areas of occupancy by IUCN (2006). Other surveys in and around the area did not locate any additional populations (Briggs and Leigh 1990; NSW NPWS 2001; J. Briggs pers. comm.).

5. The total population of Zieria adenophora includes a very low number of mature individuals (127 mature adults, when last surveyed in 2007). The population occurs in two patches located approximately 100 m apart, and separated by a 20 m high rockface. The upper section of the population experienced a 50% decline in the last four years possibly due to drought and the impact of goat grazing on seedlings. The lower section of the population, has increased since 2000, when a goat-proof fence was constructed around the population.

6. The very small number of individuals and their distribution within a single location makes Z. adenophora highly susceptible to stochastic events such as wildfire, damage associated with human access, disease, extreme weather events or severe drought. The species is potentially threatened by trampling and habitat degradation through soil disturbance and the removal of associated vegetation by goats and wallabies. This directly affects individual plants and their habitat. Goats cause damage directly to individuals, particularly seedlings by exposing the roots and by trampling. Long term effects of goats may include erosion of the shallow soils, increased weed invasion and the prevention of adequate recruitment to the population (NSW NPWS, 2001). The integrity of the goat-proof fence is inspected infrequently to ensure that it remains an effective barrier; against further goat grazing. Potential breaches to the fence caused by treefall or vandalism may therefore go undetected for some time. Given the risks associated with the known impact of grazing on the population and the uncertain security of the fence and the uncertain management practices that may accompany future changes in ownership the species is projected to undergo a future decline (J Briggs pers. comm. 2008). ‘Competition and habitat degradation by Feral Goats, Capra hircus Linnaeus 1758’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

7. Zieria adenophora is not known to occur in any conservation reserves in New South Wales. The only population occurs on leasehold and privately owned land.

8. Zieria adenophora Blakely 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,

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

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.

Professor Lesley Hughes
Chairperson
Scientific Committee
Proposed Gazettal date: 29/08/08
Exhibition period: 29/08/08 – 24/10/08

References:

Armstrong JA (2002) Zieria (Rutaceae): a systematic and evolutionary study. Australian Systematic Botany. 15, 277-463.

Blakely WF (1941) Additions to the Australian flora. Contributions from the National Herbarium of New South Wales 1, 123.

Briggs JD & Leigh JH (1990) Delineation of Important Habitats of Threatened Plant Species in South-Eastern New South Wales. Australian Heritage Commission, Canberra.

IUCN (2006) ‘Guidelines for using the IUCN Red List Categories and Criteria. Version 6.2.’ (Standards and Petitions Working Group of the IUCN Species Survival Commission Biodiversity Assessments Sub-committee: Switzerland)

NSW NPWS (2001) ‘Approved Recovery Plan for the Araluen Zieria (Zieria adenophora)’. NSW National Parks & Wildlife Service, Hurstville, NSW. Available from: http://www.nationalparks.nsw.gov.au/PDFs/approved_Zieria_adenophora.pdf

Page last updated: 28 February 2011