Bossiaea bombayensis - vulnerable species listing

Note: The Scientific Committee placed a preliminary determination for this species on public exhibition under its former name: Bossiaea sp. Bombay (K.L. McDougall 1200).

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Bossiaea bombayensis K.L.McDougall (family Fabaceae) is a recently described species (McDougall 2009). Bossiaea bombayensis was previously included within Bossiaea bracteosa sens. lat., a widespread taxon occurring on the central and southern tablelands and south coast of NSW, and in Victoria and South Australia (James and Harden 2002; McDougall 2009). Recent taxonomic research (McDougall 2009) has resulted in Bossiaea bracteosa sens. lat. being split into a number of new species, three of which are in NSW. B. bracteosa sens. strict. is now regarded as being a Victorian endemic.

2. Bossiaea bombayensis K.L.McDougall is described as a ‘wiry shrub to 1 (–1.5) m high. Cladodes flattened, winged, glabrous apart from minute hairs in the axils of the scale leaves and scattered hairs 0.2–0.5 mm long on new growth, becoming round or oval in cross-section; reproductive branches of cladodes sub-flexuose, dark green (predominantly red when young), 2.3–4.5 mm wide, winged, not becoming incised at the nodes. Leaf scales 0.7–1.2 mm long, dark brown, glabrous apart from marginal cilia. Flowers solitary at the nodes; pedicels 1.5–2.5 mm long, glabrous, obscured by floral bracts. Floral bracts imbricate, dark brown to golden brown, mostly persistent, increasing in size from outer to inner, glabrous apart from marginal hairs, especially towards the apex, the largest of the persistent bracts 1.5–2 mm long with a broadly acute apex. Bracteoles caducous. Calyx glabrous apart from hairs on the margins and inner surface of the lobes apically (occasionally also on the outer surface of lobes), green with red spots, often heavily tinged with red abaxially, 4–5 mm long including the 5 ± equal, triangular lobes 0.9–1.4 mm long, c. 1 mm wide, heavily tinged with red, often with golden brown tips. Corolla with standard 6.5–8 mm long including a claw 2–3 mm long, 9.5–11 mm wide, equal to or just exceeding other petals, deep yellow internally with red basal markings and faint red longitudinal striations radiating from the base to the edge of the lamina, predominantly deep red externally; wings 6.5–7.5 mm long including a claw 2.2–2.8 mm long, yellow, with red markings near base internally and externally, glabrous; keel 6.5–7.5 mm long including a claw 2.5–3 mm long, dark red with a pale base, glabrous. Ovary c. 5 mm long, 6–7(–8)-ovulate, glabrous; style 3.5–4 mm long. Staminal filaments 4–5 mm long, alternately red and colourless; sheath 3.5–4.5 mm long, colourless. Pods oblong, (1.4–)2–2.6 cm long, 0.4–0.6 cm wide, glabrous, red at first, ultimately dark green with thickened reddish-brown edges and red markings; stipe 1–2.5 mm long, obscured by remains of calyx. Seeds elliptic to subreniform, 2.3–2.5 mm long, 1.3–1.5 mm wide, pale brown with dark mottles. Flowering: September–October. Fruits dehisce by mid-December.’ (McDougall 2009).

3. Bossiaea bombayensis can be distinguished from other taxa within Bossiaea bracteosa sens. lat. by the following features: ‘from B. fragrans and B. milesiae by its equal to almost equal calyx lobes, from B. bracteosa by its much shorter, truncate leaf scales, and from B. grayi by its narrow, dark green cladode branches, smaller flowers and pods, alternating red and colourless staminal filaments, and general reddish appearance (of its flowers, new growth, calyx and pods)’ (McDougall 2009).

4. Bossiaea bombayensis is currently only known from the banks of the Shoalhaven River, west of Braidwood in the South Eastern Highlands Bioregion (Thackway & Creswell 1995). It has been found over a 10-16 km stretch of the river in a steeply incised valley on sandy and rocky slopes and terraces above the frequent flood line of the river (McDougall 2009). It occurs in shrubland vegetation, though rarely extends into dry sclerophyll woodland (McDougall 2009). Associated species include Callitris endlicheri, Grevillea arenaria, Lomandra longifolia, Micrantheum hexandrum, Pomaderris andromedifolia and Leptospermum polygalifolium (McDougall 2009).

5. The geographic distribution of Bossiaea bombayensis is estimated to be very highly restricted. The extent of occurrence, measured using a minimum convex polygon covering the known distribution, is estimated to be 25-55 km2. The area of occupancy is estimated to be 20-24 km2 (Scott 2008), based on 2 x 2 km grid cells, the scale recommended for assessing area of occupancy by IUCN (2008).

6. Searches of potential habitat both upstream and downstream of the known occurrence have not led to the discovery of any further populations of B. bombayensis (McDougall pers. comm. March 2008). B. bombayensis is not known from a conservation reserve and was not found in recent searches of Nadgigomar Nature Reserve, the closest reserve to the known distribution.

7. There are a moderately low number of mature individuals of Bossiaea bombayensis, as McDougall (pers. comm.) estimates that the population includes between approximately 4000 to 6000 plants, based on field reconnaissance in the Shoalhaven gorge. A range of plant sizes have been observed, suggesting that recruitment is occurring more or less continuously and is not reliant on fire (McDougall 2009).

8. Weed invasion and competition pose a current threat to the population of Bossiaea bombayensis, particularly from Cytisus scoparius (Scotch Broom), Salix spp. (Willows) and Rubus discolor spp. agg. (Blackberry) (McDougall pers. comm. March 2008). These weeds are widespread but, at present, rarely dominate the local vegetation in this area. Although parts of the habitat are affected, weeds are not currently considered to be causing decline in Bossiaea bombayensis (McDougall pers. comm. March 2008). In addition to the three problematic species already present at the site, local occurrences of Nassella trichotoma (Serrated Tussock), Ulex europaeus (Gorse) and Pinus spp. (Pine) may threaten the species in future if they invade downstream. ‘Invasion and establishment of Scotch Broom, Cytisus scoparius’ and ‘Invasion of native plant communities by exotic perennial grasses’ are listed as Key Threatening Processes under the Threatened Species Conservation Act 1995.

9. Damming of the Shoalhaven River may pose a future threat to Bossiaea bombayensis, and could affect about 80% of suitable habitat for the species (McDougall pers. comm.).

10. Bossiaea bombayensis is threatened by environmental and demographic stochasticity due to its very highly restricted distribution and the presence of all individuals within a single population. It is prone to the effects of human activities or stochastic events within a very short time period in an uncertain future, and is thus capable of becoming Critically Endangered or even Extinct in a very short time period. Whilst the known threats are not considered to be currently leading to decline in the population of Bossiaea bombayensis, a change in the status of the proposed dam will warrant a re-assessment of the status of the species.

11. Bossiaea bombayensis is currently not eligible to be listed as an Endangered or Critically Endangered species.

12. Bossiaea bombayensis K.L. McDougall is eligible to be listed as a Vulnerable species as, in the opinion of the Scientific Committee, it is facing a high risk of extinction in New South Wales in the medium-term future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:

Clause 18

The geographic distribution of the species is observed, estimated or inferred to be very highly restricted such that it is prone to the effects of human activities or stochastic events within a very short time period.

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 18/12/09
Exhibition period: 18/12/09 – 05/03/10

References:

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)

James TA, Harden GJ (2002) Bossiaea. In ‘Flora of New South Wales Revised Edition Volume 2’. (Ed. GJ Harden) pp. 510-516. (University of NSW Press: Sydney)

McDougall KL (2009) Four new species related to Bossiaea bracteosa F.Muell. ex Benth. in south-eastern Australia. Telopea. 12, 347-360

Scott J (2008) Information for Bossiaea sp. Bombay (K.L. McDougall 1200). An unpublished report to the Scientific Committee (NSW TSC Act (1995).

Thackway R, Creswell ID (1995) An interim biogeographic regionalisation for Australia : a framework for setting priorities in the National Reserves System Cooperative Program. Version 4.0. ANCA, Canberra.