Bertya opponens - vulnerable species listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the shrub Bertya opponens (F.Muell. ex Benth.) Guymer as a VULNERABLE SPECIES in Part 1 of Schedule 2 of the Act, and as a consequence, omit reference to Bertya sp. A Cobar-Coolabah (Cunningham & Milthorpe s.n., 2/8/73) from Part 1 of Schedule 2 (Vulnerable species) of the Act. Listing of Vulnerable species is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Bertya opponens (F.Muell. ex Benth.) Guymer (family Euphorbiaceae) is a shrub that has been described by James & Harden (1990) under the taxonomic synonym  Bertya sp. A as: 'Slender shrub or small tree to 4 m high with a thick, whitish to brown tomentum. Leaves mostly opposite, oblong to oblanceolate or narrow-elliptic, 10-50 mm long, 5-25 mm wide, thick, margins recurved to revolute, upper surface hairy, becoming scabrous, lower surface densely white-tomentose with prominent midrib; petiole 3-5 mm long. Flowers sessile, 1-3 male and female flowers together; bracts 4, conspicuous, narrow, 2-5 mm long, thick, yellowish-brown tomentose, 2 inner bracts obscure, heavily viscid. Perianth segments 4, broad-ovate, 5-6 mm long, mostly glabrous and viscid; female segments fused towards the base, lobes oblong-ovate. Ovary densely villous, styles 3 or 4, mostly deeply 4-lobed. Capsule ovoid to globose, 8-9 mm long, densely villous.'

2. Bertya opponens was originally described by George Bentham in 1873 as  Croton opponens. The species was later placed in the genus  Bertya by Guymer (1985). A taxonomic revision of  Bertya by Halford & Henderson (2002) considered that plants from New South Wales previously referred to as  B. sp. A (James & Harden 1990) were in fact  B. opponens. This broad circumscription of  B. opponens included plants from western New South Wales ( e.g. Cobar, Coolabah and Narrabri) as well as several disjunct populations east of the Great Dividing Range ( e.g. Gibraltar Range and Kangaroo Creek State Forest).  B. opponens in this broad sense was the subject of the 'Approved Recovery Plan for  Bertya sp. Cobar-Coolabah (Cunningham & Milthorp s.n. 2/8/73) Recovery Plan' (NSW NPWS 2002). Recent taxonomic research (Fatemi  et al. 2007) has confirmed that the Cobar, Coolabah and Narrabri populations are typical  B. opponens but the populations east of the Great Dividing Range are in fact a new, undescribed species closely related to  B. opponens and currently known as  B. sp. (Clouds Creek M. Fatemi 4).

3. Bertya opponens ranges from central Queensland south into the North Western Plains of New South Wales. Four populations are recorded in New South Wales: one from private property near Coolabah and two to the south of Narrabri including the largest population in Jacks Creek State Forest. The fourth population was known from private property near Cobar but this population has not been seen since 1982 and is possibly now extinct.

4. Bertya opponens grows on slightly elevated ridges with moderately coarse, sandy soil. The vegetation ranges from mallee shrubland to open woodland . Little is known about the reproductive biology of  B. opponens although Austen (1999) speculated that the plants are wind pollinated and relatively long-lived. Austen (1999) also noted that populations may need some form of disturbance to stimulate recruitment (e.g. fire or physical disturbance such as that associated with earthworks). Most plants of  B. opponens are believed to be killed by fire although fires may stimulate germination from the seed bank. Frequent fires on the public estates south of the Jacks Creek population may be a threat. 'High frequency fire resulting in the 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.

5. Bertya opponens has not been recorded in New South Wales from any conservation reserves.

6. In New South Wales, Bertya opponens has a highly restricted geographic distribution. Its area of occupancy is estimated to be approximately 32 km², based on the number of occupied 2 x 2 km grid cells, the scale recommended for assessment for assessing area of occupancy by IUCN (2008). These occurrences are scattered over a wide range, however, with an estimated extent of occurrence of approximately 50,000 km² in New South Wales (Copeland 2008).

7. The total known population of Bertya opponens has been estimated to include at least five million individuals (Austen 1999). The vast majority of these occur in a single population in Jacks Creek State Forest to the south of Narrabri. This population has an age structure with many adults, juveniles and seedlings.

8. At present there appears to be no evidence that the total population of Bertya opponens is undergoing a continuing decline. The western-most population near Coolabah appears to be facing a number of threats but the very large population in Jacks Creek State Forest is apparently thriving. Decline of the western population would result in a substantial reduction in the extent of occurrence of the species.

9. Bertya opponens is not eligible to be listed as a Critically Endangered species or as an Endangered species.

10. Bertya opponens (F.Muell. ex Benth.) Guymer 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

Gazettal date: 04/12/09
Exhibition period: 04/12/09 - 29/01/10

References

Copeland LM (2008) 'Conservation and taxonomic status of Bertya sp.A Cobar-Coolabah (Cunningham & Milthorpe s.n., 2/8/73 - Euphorbiaceae) in NSW.' Report to the NSW Scientific Committee, Sydney.

Fatemi M, Gross CL, Bruhl JJ (2007) The first phenetic analysis of species limits in Bertya (Euphorbiaceae).  Australian Systematic Botany 20, 448-463.

Guymer GP (1985) A name change in the genus Bertya (Euphorbiaceae).  Austrobaileya 2, 147.

Halford DA, Henderson RJF (2002) Studies in Euphorbiaceae A.L.Juss. sens. lat. 3. A revision of  Bertya Planch. (Ricinocarpeae Mull. Arg., Bertyinae Mull.Arg.).  Austrobaileya 6, 187-245.

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 (1990) Euphorbiaceae. In 'Flora of New South Wales. Vol. 1'. (Ed. GJ Harden) pp. 389-430 (University of New South Wales Press: Sydney)

NSW NPWS (2002) Approved Recovery Plan for Bertya sp. Cobar-Coolabah (Cunningham & Milthorpe s.n., 2/8/73). NSW National Parks and Wildlife Service, Hurstville NSW.