Pterostylis despectans (terrestrial herb) - critically endangered species listing
The Scientific Committee, established by the Threatened Species Conservation Act, has made a FINAL DETERMINATION to list the terrestrial orchid Pterostylis despectans (Nicholls) M.A.Clem. & D.L.Jones as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act. Listing of critically endangered species is provided for by Part 2 of the Act.
NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. Pterostylis despectans (Nicholls) M.A.Clem. & D.L.Jones (family Orchidaceae) is a terrestrial herb with flowering stems 30-80 mm tall, 6-10 basal leaves in a rosette, and 3 or 4 stem-sheathing bract-like leaves above, the rosette leaves 10-20 mm long, 6-9 mm wide. Flowers 1-6 in number, usually with up to 4 open at a time, on slender pedicels up to 15 mm long spreading widely from the stalk or recurved. Flower with galea 10-15 mm long, transparent with grey, green or brown striations. Dorsal sepal with a filiform apical attenuation 6-13 mm long, straight or upcurved. Lateral sepals deflexed, shallowly concave, united in lower half, free in apical half, tapered into long filiform parallel points 18-26 mm long, tips about 4 mm apart and often touching the soil; lateral sepal margins densely hairy. Labellum oblong-elliptic, 4-5 mm long, c. 2 mm wide, thin-textured, green to dark brown; margins entire, with one pair of erect to forward-projecting bristles c. 2 mm long near base, and 12-20 smaller spreading pale bristles 0.3-0.5 mm long. Flowering occurs in October and November. Descriptions and illustrations are available in Jones (1994: 825-6), Backhouse and Jeanes (1995: 282), Bishop (2000: 78), Jeanes and Backhouse (2000), Jeanes and Backhouse (2001: 105), and Jones (2006: 326 – as Oligochaetochilus despectans).
2. Pterostylis despectans is not easily confused with other orchid species, being characterised by the flower colours, short flower stem, long spreading pedicels, sepal points often resting on the soil, and labellum with two prominent basal bristles.
3. The species was originally named Pterostylis rufa var. despectans Nicholls, and appears under that name in sources prior to 1989, at which time it was raised to species rank as Pterostylis despectans (Nicholls) M.A.Clem. & D.L.Jones. In some recent treatments (e.g. Jones 2006; Commonwealth Species Profiles Rare and Threatened database, accessed 27 May 2007), it has been placed in the segregate genus Oligochaetochilus, as O. despectans (Nicholls) Szlach., but this generic placement is not yet widely accepted.
4. Pterostylis despectans is listed as Endangered under the Commonwealth Environmental Protection and Biodiversity Conservation (EPBC) Act, and as Threatened under the Victorian Flora & Fauna Guarantee Act 1988 (FFGA website accessed 27 May 2007, showing listings as at July 2006).
5. In New South Wales the species is known only from a single population discovered in 2005 near Moama, in the Riverina Bioregion (sensu Thackway and Cresswell 1995). The site is within the Murray Local Government Area. Several surveys of Riverina grassland and regional Travelling Stock Reserves (TSR), including McDougall et al. (1993), Benson et al. (1997), Webster (1999), and McNellie et al. (2005), did not record P. despectans and it seems likely that the species is extremely rare in New South Wales.
6. The species also occurs as very small fragmented populations in central Victoria (Maryborough-Avoca region, and a disjunct occurrence at Terrick Terrick) and in South Australia (Northern Lofty region near Mt Bryan) (Bickerton and Robertson 2000; Coates et al. 2003; Jones 2006). Coates et al. (2003) estimate the total number of individuals in the Victorian and South Australian populations as less than 1500.
7. Bickerton and Robertson (2000) describe the life history as follows: “[it] remains dormant underground as a tuber in late summer into early winter. In winter it develops a rosette of six to ten leaves. The flower stem … is produced in November … the leaves shrivel up by the time the flowers mature.” Like most Australian terrestrial orchids the species is believed to be partly or fully dependent on a mycorrhizal symbiont.
8. The New South Wales population is reported (K. McDougall in litt. 2006) as occuring in “forb-rich grassland on flat alluvial plains …The grassland appears to be natural and not derived from Acacia pendula woodland”. The only tree species recorded as present at the site is Allocasuarina luehmannii. The soil is a reddish, probably calcareous clay-loam (K. McDougall, N. Walsh, both pers. comm.).
McDougall (1993) assigns the grass/herb community at the P. despectans site to ‘Community R1.1’, which may manifest as ‘tussock grassland, herbfield or low chenopod shrubland (possibly disclimax) … May be dominated by one of many species but most frequently Danthonia setacea (pilose form)’. The community is described as occurring on plains of Quaternary alluvial sediments with an annual rainfall of 405-465 mm.
The orchid habitat at the Moama site has been mapped (DIPNR 2004) as unit ALP30 ‘Grasslands with scattered trees on alluvial plains’. McNellie et al. (2005) define the primary floristic group (including the orchid site) within this map unit as ‘Low Grasslands and/or Forblands with scattered stands of Eucalyptus microcarpa or Eucalyptus largiflorens or Allocasuarina luehmannii’, “consisting of numerous small (approximately 10 to 30 ha) and isolated and discontinuous patches within the cropping zone of the southern Riverina”.
9. Bishop (2000) describes habitat of the Victorian and South Australian populations as “woodland”, and says that the species favours “bare stony ground that bakes concrete-hard by flowering time”. Bickerton and Robertson (2000) record the South Australian populations as from “peppermint box woodland with a sparse herbaceous understorey”, and the Victorian populations as from “grassy woodland”. These records are at some variance with the NSW occurrence in apparently natural grassland or near-grassland on alluvial substrates. Future surveys should not assume grassland as the only potential habitat.
10. The Moama population has been assessed as comprising between fewer than 20 to about 60 individual plants (K. McDougall in litt., based on 2005 season; D. Jones pers. comm. 2007, based on 2006 season). All plants known to date occur within an area of about one hectare, within an apparently suitable habitat patch-size of about 20 ha (K. McDougall in litt. 2006, pers. comm. 2007).
11. Pterostylis despectans is not known to occur in any NSW conservation reserves. The single known site is in a Travelling Stock Reserve. The site is “one of the most diverse remnants of grassland vegetation in the Riverina, probably because there is no dam and stock cannot remain at the site for long” (K. McDougall in litt.), although it is “heavily grazed at times” (McDougall in litt., citing pers. comm. from M. Mullins, Deniliquin Rural Lands Protection Board). The site is currently managed for low-intensity grazing as part of a funding program for high conservation-value TSRs through the Murray Catchment Management Authority.
12. Grazing, fire and other management regimes for conservation of P. despectans have not been determined. The species may be particularly endangered by current or changed future management of stock access and grazing, especially if a stock-watering point were to be added to the site. Some grazing may be beneficial for the native vegetation of the site and total stock exclusion may be detrimental, in part because of annual exotic grasses and Romulea spp. which are encroaching from a road drain and an easement on the site (K. McDougall in litt.). McDougall (pers. comm. 2007) states that as of September 2005 Romulea was strongly associated with areas of disturbed soil in, or adjacent to, the drain and the easement, and suggests that while cockatoo digging of Romulea bulbs may be contributing to the spread of that weed by soil disturbance, a higher risk of a major spread of Romulea (and other weeds) lies in a coincidence of a rain event with a major visitation by cattle, leading to intensive soil disturbance and subsequent weed spread.
13. Natural grassland communities in the Riverina area of NSW and Victoria have undergone significant declines since the advent of European settlement and stock-grazing. McDougall et al. (1993) report high levels of decline of this general vegetation type. However, past decline of the specific habitat in which this Prasophyllum occurs in New South Wales cannot be confidently inferred as yet. It has been suggested (Benson et al. 1997:13, apropos a region to the north of the Moama site) that post-settlement declines of natural grassland communities may have been less severe on the NSW side of the border. Interstate evidence suggests that P. despectans has a wider habitat tolerance than is evident from the single known NSW site. Consequently any assessments of decline in forb-rich grassland in the southern Riverina of NSW can only be taken as, at best, a partial surrogate for assessing possible past decline of P. despectans. Nevertheless, the assignment by McDougall et al. (1993) of the Moama grass/forb community to a distinct vegetation type, that is rare and restricted in NSW but shared with at least one P. despectans site in Victoria, suggests that the Moama occurrence of P. despectans may be best regarded as a naturally isolated occurrence. This interpretation appears to be supported by the co-occurrence of P. despectans and another rare orchid known as Prasophyllum aff. occidentale sp. ‘D’ and as Prasophyllum sp. ‘Moama’ (D.L.Jones 19276), at both the Moama site and at Terrick Terrick (Vic.), in both cases within habitat assignable to ‘Community R1.1’ of McDougall et al. (1993).
14. P. despectans has been assessed as having undergone major declines since European settlement in Victoria and South Australia (Coates et al. 2003). There are no data on post-settlement decline of the species in New South Wales. The species in this State is however very highly restricted in its distribution and strongly disjunct from the nearest (Victorian) population. A decline in abundance and habitat quality is likely in the NSW population if the site is not managed to exclude threats (K. McDougall in litt.; D. Jones pers. comm. 2007). The low number of individuals (c. 20-60) also renders the population vulnerable to stochastic impacts.
15. Pterostylis despectans (Nicholls) M.A. Clem. & D.L. Jones 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) The following two 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:
(i) an index of abundance appropriate to the taxon,
(ii) geographic distribution, habitat quality or diversity, or genetic diversity;
(e) The following two 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.
Professor Lesley Hughes
Chairperson
Scientific Committee
Proposed Gazettal date: 28/03/08
Exhibition period: 28/03/08 – 23/05/08
References:
Backhouse GN, Jeanes JA (1995) ‘The orchids of Victoria.’ (The Meigunyah Press, Melbourne).
Barker WR, Barker RM, Jessop J, Vonow H (eds) (2005) ‘Census of South Australian Vascular Plants, edition 5.0’. (Botanic Gardens of Adelaide and State Herbarium, South Australia) (accessed 29 May 2007).
Bates RJ, Weber JZ (1990) ‘Orchids of South Australia.’ Flora and Fauna Handbooks Committee, Adelaide.
Benson J, Allen CB, Togher C, Lemmon J (2006) New South Wales Vegetation Classification and Assessment: Part 1, Plant communities of the NSW Western Plains. Cunninghamia 9, 383-450.
Benson JS, Ashby EM, Porteners MF (1997) The native grasslands of the Riverine Plain, New South Wales. Cunninghamia 5,1-48.
Bickerton D, Robertson M (2000) ‘Lowly Greenhood (Pterostylis despectans) 'Mt Bryan' Recovery Plan’. (Threatened Species Network, Threatened Plant Action Group, South Australia) [accessed 27 May 2007.
Bishop A (2000) ‘Field guide to the orchids of New South Wales and Victoria’. (University of New South Wales Press, Sydney)
Coates F, Jeanes J, Pritchard A (2003) ‘Recovery Plan for twenty-five threatened orchid taxa of Victoria, South Australia and New South Wales 2003-2007’. Department of Sustainability and Environment, Melbourne.
DIPNR (2004) ‘Echuca – 7825, edition 1.’ [Native Vegetation Map]. Dept of Infrastructure, Planning and Natural Resources, Wagga Wagga NSW.
Jeanes JA, Backhouse GN (2000). 'Wild Orchids of Victoria, Australia.' (CD-ROM, Zoonetics, Seaford, Vic.)
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Jones DL, Clements MA, Molloy BPJ (2002) A synopsis of the subtribe Pterostylidinae. Australian Orchid Research 4, 125-144.
Jones DL (2006) ‘A complete guide to native orchids of Australia, including the island territories.’ (Reed New Holland, Frenchs Forest NSW)
McDougall KL, Barlow T and Appleby M (1993) Grassland communities and significant grassland sites: Western Basalt Plains, Lake Omeo, Murray Valley Riverine Plains and the Wimmera. In: ‘Conservation of lowland native grasslands in south-eastern Australia’. (Eds KL McDougall and JB Kirkpatrick). World Wide Fund for Nature: Australia.
McNellie M, Greenwood G, Vanzella B, Horner G, Schliebs M, Turner B, Davy MC, Hudspith TJ, Nott TA (2005). Native vegetation map report series No. 5 Moulamein, Wanganella, Conargo, Cohuna, Mathoura, Tuppal and Echuca 1:100 000 Map Series. Unpublished report, Department of Infrastructure, Planning and Natural Resources, Wagga Wagga.
Ross, J.H. & Walsh, N.G. (2003) ‘A Census of the Vascular Plants of Victoria Edn 7.’
(Royal Botanic Gardens, Melbourne) (web version accessed 29 May 2007)
Thackway R, Cresswell ID (1995) ‘An interim biogeographic regionalisation for Australia. Version 4.0’. Australian Nature Conservation Agency, Canberra.
Webster R (1999) Flora and fauna habitat assessment of Travelling Stock Reserves within the Murray Rural Lands Protection Board. Unpublished report to Murray RLPB by Ecosystems Pty Ltd, Deniliquin.