Bossiaea fragrans - critically endangered species listing

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Bossiaea fragrans K.L.McDougall (Fabaceae) is a recently described species (McDougall 2009). Bossiaea fragrans was previously included within B. 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 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. Bossiaea fragrans is the most northern taxon of those previously included within B. bracteosa sens. lat.

2. Bossiaea fragrans is an ‘erect shrub 1–2.5 m high. Cladodes flattened, winged, becoming round or oval in cross-section but retaining remnants of wings; reproductive branches of cladodes glaucous green, oblong-linear to narrowly oblanceolate or irregular, (6–)8–14 mm wide, winged, glabrous apart from minute hairs in the axils of the scale leaves, becoming incised at the nodes. Leaf scales 1.5–1.9 mm long, dark brown, glabrous apart from marginal cilia. Flowers 1(–6) per node; pedicels 2.5–3 mm long, glabrous, exceeding persistent floral bracts by 1–2 mm at anthesis. Floral bracts imbricate, narrowly ovate, increasing in size from outer to inner, the largest of the persistent bracts c. 1.5 mm long with an acute apex, glabrous apart from marginal hairs, especially towards the apex, chestnut brown, all but a few bracts caducous prior to anthesis. Bracteoles caducous but rarely one or both present at anthesis. Calyx glabrous apart from hairs on the margins and inner surface of the lobes apically, green, 4.5–5 mm long; lobes c. 1 mm long, the 2 upper lobes c. 1.5 mm wide, rounded-truncate with acute, diverging apices, the lower 3 triangular, c. 1 mm wide, with acute apices. Corolla with standard 10.5–12 mm long including a claw 3–4 mm long, 12.5–15 mm wide, exceeding other petals, yellow internally and heavily tinged with red externally, with red basal markings and red longitudinal striations radiating from the base to the edge of the lamina; wings 10–11 mm long including a claw 3–4 mm long, yellow, with red markings near base and occasionally extending to edge of lamina, glabrous; keel 10–11 mm long including a claw 3–4 mm long, dark red, glabrous. Ovary 5.5–6 mm long, 5–6-ovulate, glabrous; style 2.5–4 mm long. Staminal filaments 4–5 mm long, red; sheath 4–5 mm long, red. Pods oblong, 2.4–3.8 cm long, 0.8–1 cm wide, glabrous, dark green with reddish-brown markings when mature; stipe 2.5–3 mm long. Seeds elliptic to sub-reniform, 3.0–3.2 mm long, 1.8–2 mm wide, dark brown. Flowering: September–October. Fruits dehisce: by December.’ (McDougall 2009).

3. Bossiaea fragrans is morphologically most similar to B. milesiae K.L. McDougall, which is confined to the Brogo River catchment near Bega, but B. fragrans has ‘broader, glaucous cladode branches, longer corollas and darker coloured standards’ (McDougall 2009). In addition, the two species occupy different habitat (McDougall 2009).

4. Bossiaea fragrans is currently only known from the Abercrombie Caves area, south of Bathurst on the NSW central tablelands. B. fragrans is very highly restricted, as only two sites, 1.5 km apart, are currently known to support extant occurrences and the species has apparently disappeared recently from a third nearby site. The extent of occurrence and area of occupancy were estimated to be 4-8 km2, based on 2 x 2 km grid, the spatial scale of assessment recommended by IUCN (2008). The populations occur just within the boundary of the South Western Slopes Bioregion, though the species may also occur in the South Eastern Highlands Bioregion (sensu Thackway and Creswell 1995).

5. The two extant occurrences of Bossiaea fragrans are located within the Abercrombie Karst Conservation Area, a conservation reserve managed by NSW National Parks and Wildlife Service. The plants occur within an open White Box (Eucalyptus albens) Woodland on slate and volcanic substrates. B. fragrans was first collected in this area in 1955, and the scarcity of herbarium collections of this taxon suggests that it may have been historically rare and restricted in its occurrence (National Herbarium of NSW records). Recent searches of suitable habitat in the Abercrombie Karst Conservation Area have not led to the discovery of any further populations. Aerial photographs of the surrounding areas indicate there are some large wooded remnants in the vicinity of Abercrombie Caves, but the landscape is generally cleared and modified for farming (McDougall pers. comm. March 2008).

6. The number of mature individuals of Bossiaea fragrans is extremely low. Recent searches have located a total of 13 plants within the two extant populations (12 plants at one site, and only one plant at the second site, although a persistent seed bank may be present in the soil). A third site with two plants was recorded in 2003, but the species could not be found at the same location in 2005 (McDougall pers. comm.). There may be a seedbank present in the soil at all three sites as Bossiaea species typically have a long-lived seedbank that responds to fire (Auld pers. comm. May 2008). However, there are thought to have been no fires in the area since 1939 (McDougall pers. comm.) and recent observations suggest that seed predation is significant. The seedbank may therefore be of limited size and viability. Seedling recruitment in the interfire intervals is likely to be limited (Auld pers. comm. May 2008), and seedlings may be subject to grazing.

7. Bossiaea fragrans is threatened by grazing and competition from weeds. Goats are common in the Abercrombie Caves area and it is thought that they may be grazing on B. fragrans seedlings (McDougall pers. comm.). ‘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. The grass Serrated Tussock (Nassella trichotoma) is also in the area and may be a threat to recruitment of seedlings (McDougall 2009). Serrated Tussock forms large tussocks and mature plants droop across the ground smothering other plants (DECC 2008). ‘Invasion of native plant communities by exotic perennial grasses’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

8. Bossiaea fragrans is threatened by environmental and demographic stochasticity due to its very highly restricted distribution and small population size. As a result of the above mentioned threats, B. fragrans is at risk of a projected decline in abundance, geographic distribution or habitat quality.

9. Bossiaea fragrans 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:

(i) an index of abundance appropriate to the taxon

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

(e) and the following conditions apply:

(i) the population or habitat is observed or inferred to be severely fragmented;

(ii) all or nearly all mature individuals are observed or inferred to occur within a small number of populations or locations.

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

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

(e) and the following conditions apply:

(i) the population or habitat is observed or inferred to be severely fragmented;

(ii) all or nearly all mature individuals are observed or inferred to occur within a small number of populations or locations.

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

Gazettal date: 18/12/09
Exhibition period: 18/12/09 – 29/01/10

References:

DECC (2008) Invasion of native plant communities by exotic perennial grasses as a key threatening process – an overview (PDF 115KB). Department of Environment and Climate Change Threatened Species Information. Fact sheet on exotic perennial grasses.Accessed 26th October 2009.

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.

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.