Tylophora linearis - vulnerable species listing
The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the vine Tylophora linearis P.I.Forst. as a VULNERABLE SPECIES in Part 1 of Schedule 2 of the Act, and as a consequence, to omit reference to Tylophora linearis P. Forster from Part 1 of Schedule 1 (Endangered 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. Tylophora linearis P.I.Forst. (family Apocynaceae), based on information given in Harden & Williams (1992) and Forster et al. (2004), is described as follows: Slender almost glabrous twiner, latex clear. Leaves with lamina linear, 1-5 cm long, 0.5-3 mm wide, apex shortly acute, base gradually attenuate into the petiole; lamina flat but the margins incurved at the base; glands usually absent from the base of the midvein; petiole 0.6-3 mm long. Flowers purplish inside, 3-6 mm in diam., corolla lobes ovate or narrow-ovate, 2-3 mm long; in umbels of 3-8 flowers, usually simple, occasionally 2 together on a common peduncle; peduncles 4-8 mm long, pedicels slender, 2.5-5 mm long. Fruit fusiform, 95-100 mm long, c. 5 mm diameter, glabrous.
2. Tylophora linearis was originally described by Forster (1992) from the Temora district in central NSW. This description was based on limited collections of relatively old herbarium specimens. A more accurate account of the morphology was later given by Forster et al. (2004), which included the first description of the fruit and several corrections to earlier descriptions of the growth habit and latex colour. For example, the earlier description of the latex as milky (Forster 1992) was erroneous. The species was previously included within the family Asclepiadaceae which is now regarded as a subfamily (i.e. Asclepiadoideae) within the plant family Apocynaceae.
3. Tylophora linearis occurs from southern Queensland into central NSW as far south as Temora. Most records are from the Dubbo region with scattered populations also recorded in the Baradine and Barraba districts. At the time of the original description in 1992, just four localities were known, but targeted searches in 2003 revealed several additional populations in Goobang National Park, Coolbaggie Nature Reserve, and Eura, Pilliga West, Cumbil and Goonoo State Forests (Forster et al. 2004). The total number of confirmed populations now stands at 10 although it is considered likely that other unconfirmed records may also be referred to this species (Copeland 2008).
4. Tylophora linearis grows in dense shrublands occasionally overtopped by Callitris glaucophylla and various species of Eucalyptus. Melaleuca uncinata appears to be the most common shrub in the habitat of the Tylophora linearis populations around Dubbo. Most populations occur on the western slopes of NSW with some possibly occurring in flatter terrain on the western plains. Altitudes are generally in the range of 300-400 m above sea level. Tylophora linearis apparently has the ability to survive fires as it has been observed resprouting from the lower stems within 12 months of a moderately intense wildfire (Forster et al. 2004). Variation in flowering is uncertain, but suspected to be partly related to rainfall. As with most asclepiads, T.linearis is assumed to be insect-pollinated (Forster et al. 2004).
5. Tylophora linearis has been recorded from a number of conservation reserves including Coolbaggie Nature Reserve, Goonoo Community Conservation Area and Goobang National Park.
6. Tylophora linearis has a highly restricted geographic distribution. Its area of occupancy is estimated to be approximately 36 km2 based on 2 x 2 km grids, the spatial scale of assessment recommended by the IUCN (2008). These occurrences are scattered over a wide range, however, with an estimated extent of occurrence of approximately 65000 km2 in New South Wales (Copeland 2008).
7. The total population of Tylophora linearis in New South Wales is estimated to include at least 250-500 mature individuals (Copeland 2008). However, no data are available to estimate the size of several of the known populations and estimates are also complicated by difficulties in positively identifying plants that may not be flowering at the time of survey. Although the total population of Tylophora linearis may be larger than current estimates suggest, there are unlikely to be more than 1000 mature individuals.
8. At present there appears to be no evidence that Tylophora linearis is undergoing a continuing decline, although it is at risk from stochastic events as a result of its small population size. Most populations of the species occur in protected areas or areas within state forests which are unsuitable for logging.
9. Tylophora linearis is not eligible to be listed as an endangered or critically endangered species.
10. Tylophora linearis P.I.Forst. 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 17
The total number of mature individuals of the species is observed, estimated or inferred to be:
(c) low.
Professor Lesley Hughes
Chairperson
Scientific Committee
Proposed Gazettal date: 21/11/08
Exhibition period: 21/11/08 – 23/01/09
References
Copeland LM (2008) ‘Conservation status of Tylophora linearis P.I.Forst. in New South Wales.’ Report to the NSW Scientific Committee, Sydney.
Forster PI (1992) A taxonomic revision of Tylophora R.Br. (Asclepiadaceae: Marsdenieae) in Australia. Australian Systematic Botany 5: 29-51.
Forster PI, Binns D, Robertson GR (2004) Rediscovery of Tylophora linearis P.I.Forst. (Apocynaceae: Asclepiadoideae) from New South Wales, with revision of its conservation status to vulnerable. Austrobaileya 6(4): 941-947.
Harden GJ, Williams JB (1992) Asclepiadaceae. In ‘Flora of New South Wales. Vol. 3’. (Ed. GJ Harden) pp. 525-537 (University of New South Wales Press: Sydney).
IUCN (2008) ‘Guidelines for using the IUCN Red List categories and criteria. vers. 7.0.’ Prepared by the Standards and Petitions Working Group of the IUCN SSC Biodiversity Assessments Sub-Committee.