Pomaderris walshii - critically endangered species listing
The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the shrub Pomaderris walshii J.C. Millott & K.L. McDougall 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. Pomaderris walshii J.C. Millott & K.L. McDougall (family Rhamnaceae), is a shrub or small tree to 3 m tall. The young stems, petioles, leaf undersurfaces and outer surface of the flowers are covered with a layer of white stellate hairs mixed with loosely appressed silvery white or rusty simple hairs. The leaves are narrowly ovate, about 36-60 mm long, 14-22 mm wide, with a cuneate to obtuse base; margins entire and flat or slightly recurved; apex acute to acuminate; adaxial (upper) surface green and hairless; abaxial (lower) surface with the lateral veins clearly evident and marked by rusty simple hairs. Flowers are 200-100 together in pyramidal to hemispherical terminal heads 4-7.5 cm long and wide at the base; individual flowers are cream to yellow, externally pubescent to villous; pedicels 1.5-4.3 mm long; hypanthium 0.8-1.2 mm long, 0.8-1.4 mm in diameter; sepals 1.8-2.0 mm long; petals 1.7-1.9 mm long, spreading, spathulate; stamens 2-2.5 mm long; anthers 0.7-1.2 mm long; ovary inferior, summit pubescent with simple hairs; style hairless, 1.6-1.9 mm long, branched in lower or middle third. A more detailed description is given in Millot and McDougall (2005).
2. Pomaderris walshii is thought to be most closely related to P. nitidula (Benth.) N.A. Wakef., from which it differs in its greater stature, smaller flowers, and more obtuse leaf lamina base. P. nitidula occurs on the North Coast and Northern Tablelands of New South Wales, with the most southerly known occurrence at Gloucester Tops, some 300 km from the P. walshii locality. P. walshii differs from P. argyrophylla N.A. Wakef. sens. str. in its more obtuse leaf base, shorter leaves, and details of leaf vein indumentum; from P. graniticola N.A. Wakef. K.L. McDougall & J.C. Millott (formerly P. argyrophylla subsp. graniticola N.A. Wakef.) in its broader inflorescence, larger leaves, and leaf vein indumentum; and from P. parrisiae N.G. Walsh in these same characters. Delimitation of the species based on morphometric analysis is discussed in Millot and McDougall (2005).
3. Pomaderris walshii has a very highly restricted distribution. It is currently known only from the upper catchment of the Kangaroo River, above the escarpment near Robertson within the Sydney Basin Bioregion (Thackway and Creswell 1995). It occurs as two small populations within a total area of occurrence of about three lineal kilometres of riparian habitat, with very low numbers of individuals.
4. One population occurs in a conservation reserve, Budderoo National Park, with 13 known individual plants (Millot and McDougall 2005). This population occurs in riparian shrubland dominated by Callicoma serratifolia, Ceratopetalum apetalum, and Grevillea rivularis, in an area known to have last been burnt in 1983. The second population occurs on private freehold land upstream, comprises about 30 individual plants (Millot and McDougall 2005), and occurs in disturbed open grassy forest dominated by Eucalyptus fastigata, partly cleared for grazing. An unvouchered survey record (Jordan 1989) of an undescribed Pomaderris species close to Carrington Falls reports a habitat of Eucalyptus piperita/ E. sieberi forest, but this occurrence has not been relocated and it is unclear whether it relates to P. walshii. Survey efforts in the general area of Carrington Falls have been reasonably intensive and have not disclosed any more populations (K. McDougall, pers. comm.). Identification of other possible areas of habitat on the Illawarra escarpment would be desirable, followed by further survey.
5. The habitat constraints, ecology, and reproductive biology of P. walshii are very poorly known. Fruit and seed are not yet reported and it is possible that the plants do 'not reliably produce fruit, which is unusual in this genus' (N. Walsh, National Herbarium of Victoria, pers. comm., 14 April 2005). Millot and McDougall (2005) suggest a possible capability for resprouting following flood damage. They also report that the population in Budderoo National Park is mostly 'apparently young', suggestive of cohort recruitment. Patterns of fecundity, recruitment, longevity, genetic variation and fitness, and self-pollination capability are not known. The response of the species to pathogens is unknown.
6. Threats operating at the Budderoo National Park site may include flooding, as the habitat is riparian and the area has a relatively high rainfall of about 1800 mm p.a. Millot and McDougall (2005) report apparent flood damage. Changed fire regimes may represent a threat, as may genetic consequences of small population size. Climate change and its effects on habitat may constitute a threat as the area is highly dependent on orographic rainfall. Potential or actual threats operating at the second, private tenure site include all of the above, plus the possibility of changed land use. These threats together with the very low numbers and very restricted area of occupancy are likely to lead to future decline.
7. Pomaderris walshii J.C. Millott & K.L. McDougall 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 either:
(i) an index of abundance appropriate to the taxon, or
(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 either:
(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
Clause 17
The total number of mature individuals of the species is observed, estimated or inferred to be:
(a) extremely low.
Associate Professor Lesley Hughes
Chairperson
Scientific Committee
Proposed Gazettal date: 20/04/07
Exhibition period: 20/04/07 - 15/06/07
References
Anderson RH (1961) Introduction. Contributions from the New South Wales National Herbarium Flora Series 1-18: 1-15
Jordan P (1989) Grevillea rivularis (Unpublished report, NSW National Parks & Wildlife Service, Hurstville).
Millot JC, McDougall KL (2005) A new species of Pomaderris (Rhamnaceae) from the Central Tablelands of New South Wales. Telopea 11, 79-86
Thackway R, Creswell ID (1995) (eds) An interim biogeographic regionalisation of Australia: a framework for establishing the national system of reserves version 4.0. (Australian Nature Conservation Agency: Canberra).