Rotala tripartita (a herb) - endangered species listing
The Scientific Committee, established by the Threatened Species Conservation Act, has made a FINAL DETERMINATION to list the herb Rotala tripartita Beesley as an ENDANGERED SPECIES in Part 1 of Schedule 1 of the Act. Listing of endangered species is provided for by Part 2 of the Act.
NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. Rotala tripartita Beesley (family Lythraceae) is described by Highet and Wilson (2007) as an annual or short-lived perennial herb up to 40 cm tall, with branched stems that are often shortly creeping at the base of the plant and erect above. Leaves are glabrous, opposite, sessile, ovate to lanceolate, up to 20 mm long and 5 mm wide with the lower surface paler than the upper surface. Flowers are sessile, solitary in axils of bracts and scattered along stems. The hypanthium is c. 1 mm long. Flowers have three (or rarely four) sepals with appendages longer than sepals, three (or rarely four) elliptic, colourless petals and three (or rarely four) stamens inserted near the base of the hypanthium. The style is c. 0.5 mm long. Capsules are globose, c. 1.5 mm long with three valves.
2. Rotala tripartita occurs in New South Wales, Queensland and the Northern Territory. In New South Wales the species is currently known from only two locations, one in the Casino district and one in the South Grafton area, in the northern part of the North Coast bioregion ( sensu Thackway and Creswell 1995). These locations are separated by a distance of less than c. 100 km. The geographic distribution (extent of occurrence) of the species in New South Wales is therefore highly restricted. There are no records of Rotala tripartita in any reserve or State Forest.
3. Rotala tripartita is a riparian species that grows in free-standing water with sedges. Data on population sizes of Rotala tripartita at the two locations in New South Wales are scant. Recent surveys, however, have provided some early information on the population in the South Grafton area. There appear to be extreme fluctuations in abundance of the species, with plants observed to germinate prolifically and establish in large numbers after substantial rainfall. Individuals disappear above-ground during dry periods and may only persist during these times in the seed-bank.
4. Surveys in the South Grafton area located two individuals of Rotala tripartita growing in exposed silty clay at the edge of a dam, c. 24 km south-west of Grafton. Both of these individuals disappeared during prolonged drought. The species was then located in large numbers at the edge of a second dam, to the south and c. 150 m upstream of the initial occurrence. A single robust individual (flowers and seeds present) was found growing in Melaleuca freshwater coastal wetland (an area known as Black Swamp), located in a separate creek system c. 2 km south-west of the locality described above. A second individual (flowers and seeds present) was located within the Black Swamp wetland, c. 150 m south of the other Black Swamp individual.
5. Rotala tripartita is threatened in New South Wales by environmental stochasticity due to its highly restricted geographic distribution and small number of locations. The species is further threatened at Black Swamp in South Grafton by the construction of an access road and a cleared alignment for a pipeline and powerline to a proposed dam. This construction work is likely to result in sedimentation and changes to downstream swampland.
6. Projected reduction in rainfall in New South Wales as a result of climate change may also threaten the species’ habitat (Hennessy et al. 1997). ‘Anthropogenic climate change’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.
7. Rotala tripartita Beesley is not eligible to be listed as a critically endangered species.
8. Rotala tripartita Beesley is eligible to be listed as an endangered species as, in the opinion of the Scientific Committee, it is facing a very high risk of extinction in New South Wales in the near 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:
(b) highly restricted,
and
(e) the following conditions apply:
(ii) all or nearly all mature individuals are observed or inferred to occur within a small number of populations or locations,
(iii) extreme fluctuations are observed or inferred to occur in
(A) an index of abundance appropriate to the taxon.
Professor Lesley Hughes
Chairperson
Scientific Committee
Proposed Gazettal date: 28/03/08
Exhibition period: 28/03/08 – 23/05/08
References
Hennessy KJ, Gregory JM, Mitchell JFB (1997) Changes in daily precipitation under enhanced greenhouse conditions. Climate Dynamics 13, 667-680.
Highet J, Wilson PG (2007) (13/03/07) Rotala tripartita, in PlantNET - The Plant Information Network System of Botanic Gardens Trust, Sydney, Australia (version 2.0). http://plantnet.rbgsyd.nsw.gov.au
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)