Dodonaea stenozyga - critically endangered species listing

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the shrub Dodonaea stenozyga F.Muell., as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act, and as a consequence, to omit reference to Dodonaea stenozyga F.Muell. 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. Dodonaea stenozyga, (family Sapindaceae) is described by West (1984) as a: “Dioecious erect, rounded and compact shrub, 0.5-1.5 m high. Branches erect; branchlets angular, often 4-angled, glabrous. Leaves paripinnate, sometimes terminated by a very small tooth or lobe, including the petiole (0.9-) 1.5-3 (-3.8) cm long; petiole (9.5-) 12.5-20 (-24) mm long, terete, glabrous; rhachis to 1 mm broad, terete; leaflets 2-6 (-10), opposite or irregularly alternate, linear, iterete or concave or channelled above, often falcate or sometimes ±flat and straight, (8-) 9-13.5 (-25) x 0.5-1(-2) mm, coriaceous, viscous, with flat glands, glabrous, not restricted at the base, margin entire, apex obtuse, often recurved, midvein visible above, obscure below. Inflorescence usually a diad or triad, rarely a monad, axillary. Flowers unisexual; pedicels (4-) 6-7.5 (-8.5) mm long, glabrous. Sepals 4, oblong-lanceolate in female flowers, ovate in male flowers, (1.5-) 2-3 (-3.2) x 1-1.3 (-1.8) mm, usually smaller in female than in male flowers, acute to acuminate, viscous, caducous, outer surface with flat glands, glabrous, inner surface villous; at anthesis in female flowers valvate and slightly recurved at the apex. Stamens 7-8, shorter than the sepals; filament 0.2-0.4 (-0.5) mm long; anther 1.8-2 (-2.5) x 0.7-1 mm; apical appendage triangular-acute, sometimes obtuse and lobe-like, incurved, to 0.2 mm long, glabrous; in female flowers rudimentary stamens sometimes present. Ovary 4-carpellate, oblong-obovoid, 1-1.2 x 0.9-1.1 mm, glabrous; stylar elements 4, 3-4 (-5) mm long, glabrous, free over distal 0.2 mm. Capsule 4-winged, broad-elliptic or broad-obovate in lateral view, (8.5-) 10.5-13.5 (-14.5) x (10-) 11.5-l4 (-17) mm, glabrous, purple-brown or red to black at maturity, base cordate, apex obcordate; pericarp on body of carpel coriaceous; wing extending (3-) 3.5-6 (-6.5) mm beyond body of carpel, extending from base to apex of carpel, coriaceous; dehiscence septifragal. Seeds 2-4, lenticular, 1.7-2 x 1.6-1.8 mm, black, shiny; aril absent. Seedling glabrous or rarely sparsely puberulent; hyptocotyl 6-10 mm long; cotyledons linear, (7.5-) 9-12.5 x 1.5 (-2) mm, acute, glabrous; epicotyl 0.5-1 mm long; the first 2-6 leaves imparipinnate with 3-5 oblong-oblanceolate leaflets, otherwise as in mature leaves”.

 

2. Dodonaea stenozyga is closely related to D. concinna and can be distinguished by its longer leaves, with petioles greater than 9 mm long and smaller number of leaflets (West 1984).

 

3. First collected along the Darling River prior to 1859, Dodonaea stenozyga had not been recorded since then and was presumed extinct until 1998 when it was recorded at Nanya Station, north-west of Wentworth, in far south-western NSW. The species is widespread in southern Australia, from southern Western Austraila, through South Australia to western Victoria (West 1985).

 

4. Dodonaea stenozyga is found in semi-arid mallee scrub or open eucalypt woodland, often on sandy soil (West 1984; West 1985; Pressey et al. 1990; Walsh & Entwisle 1999).

 

5. Dodonaea stenozyga produces flowers and mature capsules in spring to early summer (September to December) (West 1984). Fruits are dark red and winged.

 

6. Dodonaea stenozyga has a very highly restricted geographic distribution in NSW. The entire distribution of the species falls within one or possibly two 2 x 2 km grid cells, the spatial scale recommended for estimation of area of occupancy by IUCN (2008).

 

7. The number of mature individuals of Dodonaea stenozyga is extremely low. Despite survey efforts in suitable habitat within the Scotia region, including Nanya Station (Westbrooke et al. 1998, M. Westbrooke pers. comm. November and December 2008) only one individual plant has been recently confirmed in NSW since the original collection prior to 1859 and a record of two additional plants is yet to be confirmed (M. Westbrooke pers comm. December 2008). Hence the number of mature individuals of the species is possibly one and almost certainly less than 50.

 

8. Like many Dodonaea species, standing plants of D. stenozyga are likely to be killed by fire with post-fire regeneration occurring only from seed (Hodgkinson and Oxley 1990). Consequently, the species may be susceptible to short or very long intervals between successive fires. ‘High frequency fire resulting in disruption of life cycle processes in plants and animals and loss of vegetation structure and composition’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

 

9. Feral goats are periodically abundant within the Scotia region. While the palatability of Dodonaea species may be limited, soil disturbance associated with goat activity may limit seedling recruitment of this and other plant species. ‘Competition and habitat degradation by Feral Goats, Capra hircus’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

 

10. Suitable habitat areas of Dodonaea stenozyga may have been cleared in the past in NSW (Porteners & Robertson 2003), and as a woody species with a superficial resemblance to Turpentine (Eremophila sturtii) and Narrow-Leaf Hopbush (Dodonaea viscosa), D. stenozyga could be mistaken for woody species that are subject to approved clearing as invasive native shrubs under the Native Vegetation Act 1999 (Porteners & Robertson 2003). Further clearing is unlikely to occur on Nanya Station while under management of the University of Ballarat. However, if unrecorded populations of D. stenozyga exist in the region, they may be susceptible to vegetation clearing for sand mining or pasture development. ‘Clearing of native vegetation’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.

 

11. The very small number of individuals and their distribution within a single location makes Dodonaea stenozyga highly susceptible to stochastic events such as wildfire, damage associated with human access, disease, extreme weather events or severe drought.

 

12. This species is at the edge of its distribution in NSW. As the remaining population is extremely small and isolated from other populations in South Australia, it is likely that the population of Dodonaea stenozyga has become severely fragmented. Habitat clearing may also have resulted in some fragmentation of the population, however large areas of mallee vegetation persist in south-west NSW.

 

13. Dodonaea stenozyga F.Muell. 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, or

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

(e) 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, or

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

(e) 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

Proposed Gazettal date: 11/12/09

Exhibition period: 11/12/09 – 05/02/10

 

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). (http://intranet.iucn.org/webfiles/doc/SSC/RedList/RedListGuidelines.pdf).

 

Hodgkinson KC, Oxley RE (1990) Influence of fire and edaphic factors on germination of the arid zone shrubs Acacia aneura, Cassia nemophila and Dodonaea viscosa. Australian Journal of Botany 38, 269-279.

 

Mueller FJH (1859) Dodonaea stenozyga F. Muell. In ‘Fragmenta Phytographiae Australiae’ 1: 98.

 

Porteners M, Robertson G (2003) ‘Threatened Plants in Western New South Wales: Information Review.’ NSW National Parks and Wildlife Service, Hurstville.

 

Pressey RL, Cohn JS, Porter JL (1990) Vascular plants with restricted distributions in the Western Division of New South Wales. Proceedings of the Linnean Society of New South Wales 112, 213-227.

 

Walsh NG, Entwisle TJ (1999) ‘Flora of Victoria; Volume 4, Dicotyledons Cornaceae to Asteraceae.’ (Inkata Press: Melbourne).

 

West JG (1984) A revision of Dodonaea Miller (Sapindaceae) in Australia. Brunonia 7, 1-194.

 

West JG (1985) Sapindaceae. 29. Dodonaea. In: ‘Flora of Australia’ (Ed AS George) pp 114-153. (Australian Government Publishing Service).

 

Westbrooke ME, Miller JD, Kerr MKC (1998) The vegetation of the Scotia 1:100 000 map sheet, western New South Wales. Cunninghamia 5, 665-684.

 

Page last updated: 28 February 2011