Recovery Plan for Three Orchid Species in South Australia and Victoria: Caladenia richardsiorum (Little Dip Spider-orchid) Caladenia calcicola (Limestone Spider-orchid) Pterostylis tenuissima




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Part C: Species Information

3.0 Caladenia richardsiorum D.L.Jones (Little Dip Spider-orchid)

3.1 Description


Caladenia richardsiorum is a perennial spider-orchid with a lanceolate leaf 16-22 cm in length and densely hairy on both laminae. Its generally singular yellowish-green flower, up to 40 mm wide, arises from a stem 20-40 cm in length. Sepals have prominent but short blackish clubs 8-10 mm long. The labellum is greenish-cream with maroon calli and toothed margins. Flowering occurs from late September to early November, the orchid remaining dormant when conditions are unsuitable (Jones 1991).

Caladenia richardsiorum has affinities with C. hastata, a nationally Critically Endangered species endemic to south-western Victoria. Caladenia hastata can be distinguished by a much smaller leaf, whiter flower, and slimmer sepals and petals. Both sepals and petals possess clubs 10 – 22 mm long (Jones 1991).

3.2 Conservation Status


Caladenia richardsiorum is listed as nationally Endangered under the Commonwealth EPBC Act, and as Endangered in South Australia under the National Parks and Wildlife Act 1972 (NPW Act).

3.3 Distribution and Population Size


Caladenia richardsiorum is endemic to the South East Herbarium Region, South Australia, and is found in coastal vegetation primarily between Southend and the Coorong and no more than six kilometres from the coast (Figure 1). A new sub-population was identified and formally determined in 2004 near Meningie by D Jones (CSIRO Canberra), however, the sub-population was resurveyed in 2007 and re-determined as C. saxatilis (R. Bates pers. comm. 2008). Further work is needed to clarify this sub-population. The species has a distribution from Southend to Meningie of approximately 900 km2, and occupies no more than 10 km2.

The total estimated number of mature plants of C. richardsiorum is 11,075, consisting of 46 sub-populations (Table 4). The high number of sub-populations is a reflection of the highly fragmented distribution of C. richardsiorum habitat. A number of anecdotal records exist in addition to the sub-populations outlined in this document. The validity of these records will be investigated during the implementation of this recovery plan.


3.4 Habitat


Caladenia richardsiorum is found in several coastal and sub-coastal vegetation types along the Limestone Coast of South Australia. At Nora Creina and in Canunda National Park it occurs in Coast Daisy-bush (Olearia axillaris) – Coast Beard-heath (Leucopogon parviflorus) shrubland complex (Croft et al. 1999). Associated species include Thyme Riceflower (Pimelea serpyllifolia), Bower Spinach (Tetragonia implexicoma), Coast Swainson-pea (Swainsona lessertiifolia) and Coast Velvet-bush (Lasiopetalum discolor). This complex of vegetation ranges from low coastal heathland on exposed cliff tops to shrubland on the protected side of coastal fore-dunes and is significant as it supports the larger and denser sub-populations of C. richardsiorum.

Caladenia richardsiorum also occurs in deep leaf litter under open White Coast Mallee (Eucalyptus diversifolia ssp. diversifolia) in the Robe and Beachport regions. Associated understorey and groundcover species include Coast Beard-heath, Old Man’s Beard (Clematis microphylla), Stinking Pennywort (Hydrocotyle laxiflora) and Coast Velvet-bush. At Potters Scrub, Coorong National Park, C. richardsiorum occurs under a dense low White Coast Mallee and Golden Wattle (Acacia pycnantha/leiophylla) with a sparse understorey dominated by the weed species Bridal Creeper (Asparagus asparagoides).

On council land at Beachport it also occurs under Dryland Tea-tree (Melaleuca lanceolata) – Drooping Sheoak (Allocasuarina verticillata) low woodland. Here, associated species include Golden Wattle, Myrtle Wattle (Acacia myrtifolia), Coast Beard-heath (Leucopogon parviflorus), Sea Box (Alyxia buxifolia), Coast Cherry (Exocarpos syrticola), Coast Pomaderris (Pomaderris paniculosa), Pale Turpentine Bush (Beyeria lechenaultii), Muntries (Kunzea pomifera) and Blunt Leaf Ground-berry (Acrotriche cordata).



Occupied habitats within the known extent of occurrence of the species are considered to be habitat critical to the survival of C. richardsiorum. Preventing any further fragmentation of existing vegetation that supports this species will be crucial to its long-term survival.

Table 4. Reserved and unreserved sub-populations of Caladenia richardsiorum.

Location

Manager

No. of individuals

No. of sub-populations

Year

Reserved Sub-populations 

Canunda National Park, Southend, SA

DEWNR

117

3

2006

Little Dip Conservation Park, Robe, SA

<107

7

2007

Coorong National Park, SA (to be validated)

200

1

2004

Total Reserved

424

11

 

Unreserved Sub-populations 

Nora Creina 1, SA

Private Property

1188

1

2003

Nora Creina 2, SA

5

1

2002

Nora Creina 3, SA

50

1

2002

Nora Creina 4, SA

219

3

2002

Nora Creina 5, SA

5400

6

2002

Sunland 1, SA

49

4

2007

Robe Heritage Agreement, SA

97

1

2007

Coorong Private land

3005

6

2010

Beacon Hill Council Reserve, Robe, SA

Robe District Council

<10

1

2004

Pool of Siloam, Beachport, SA

Wattle Range District Council

30

1

2002

Lanky's Well, Beachport, SA

189

2

2007

Rivoli Bay, Beachport, SA

240

2

2007

Woolly Lake, Beachport, SA

5

3

2006

Lake George, Nora Creina, SA

49

1

2002

Roadside, Nora Creina, SA

67

2

2002

Total Unreserved

10603

35

 


3.5 Ecology

3.5.1 Mycorrhizae

Currently the mycorrhizal fungi have not been isolated for C. richardsiorum; however, techniques for isolating mycorrhizal fungi for the propagation of other Caladenia species are well established.
3.5.2 Pollination

In the spring of 2000, most sub-populations were naturally pollinated and producing seedlings. The pollination rate at Nora Creina was estimated to be around five percent.

In 2006, pollinator baiting was conducted to identify the wasp pollinator of C. richardsiorum. Initially the pollinator was identified as Phymatothynnus near pygidialis, which was also found to pollinate the morphologically distinct C. fragrantissima in south-west Victoria (C. Bower pers. comm. 2007; G. Brown pers. comm. 2007). However, field pollinator choice tests have shown that two wasps with very slight morphological differences responded differently to the two orchids, suggesting the wasps have different sex pheromones and the orchids have different allomones, and indicating that the two wasps are likely to belong to two closely related cryptic species (C. Bower pers. comm. 2007). The wasp species attracted to C. richardsiorum was found to be relatively common in south-west Victoria (C. Bower pers. comm. 2007). It is currently assumed that the pollinator is also relatively common in South Australia as there is a comparatively good pollination rate at most sub-populations. The pollinator abundance will be confirmed in future pollinator baiting trials. Based on the results of field trials and the pollination rate at natural sub-populations, it is considered unlikely that pollinator abundance is limiting the distribution and abundance of C. richardsiorum (Bower 2007).


3.6 Threats


Threats common to all species are outlined earlier in this document. Threats relating specifically to this species are:

  • Vegetation clearance and fragmentation. Clearance for intensive coastal development, leading to fragmentation and isolation of sub-populations.

  • Environmental weed invasion by, but not limited to: the common and Western Cape forms of Bridal Creeper (Asparagus asparagoides), Myrtle-leaf Milkwort (Polygala myrtifolia), Blue Periwinkle (Vinca major), Italian Buckthorn (Rhamnus alaternus), Coast Wattle Acacia longifolia subsp. sophorae, Coast Tea-tree (Leptospermum laevigatum), Gazania (Gazania linearis), Freesias (Freesia spp.) and Bluebell Creeper (Billardiera heterophylla).

  • Grazing. Grazing by rabbits threatens some sub-populations in the Canunda region. Warren construction and diggings can also threaten orchid sub-populations. Herbivory by exotic terrestrial snails may also threaten some sub-populations as they have been found in abundance at some coastal sites. Grazing by Western Grey Kangaroo (Macropus fuliginosus) has the potential to be a problem in the Nora Creina area – a reduction of kangaroo numbers is being undertaken under the licence of DEWNR. Sheep grazing also threatens one of the largest sub-populations at Nora Creina. As this site is privately owned, ongoing negotiations with the owner are critical.

  • Site disturbance. Visitor impacts from recreational vehicles (e.g. four-wheel drives and motorbikes) and pedestrian traffic, including naturalists and field officers, are considered a threat for some sub-populations. Visitation is very high in the Robe district and at least one sub-population is threatened from off-road vehicles driving across sensitive coastal vegetation to gain access to the beach.

  • Illegal collection. Collecting of the species by plant enthusiasts is considered a moderate threat as C. richardsiorum is an attractive species with many easily accessible sub-populations.

3.7 Previous Recovery Actions


Staff have been employed to plan and implement recovery of C. richardsiorum between 2000 and 2002 and then again between 2004 and 2010. Recovery actions have also been undertaken by DEWNR Staff.

The following management actions were undertaken:



  • Baseline data collected between 2000 and 2009, including sub-population number, site and habitat descriptions.

  • Monitoring plots established and surveys undertaken for additional sub-populations, including a survey with NOSSA of a property adjacent to the Coorong, in which an additional 3005 individuals were found in six sub-populations.

  • Site management statements for Lanky’s Well Council Reserve, Beachport; and a Heritage Agreement property near Robe were completed in 2008.

  • Weed control activities carried out since 2000 on public and private land. All weed issues are on-going. Blue Periwinkle, Myrtle-leaf Milkwort, Italian Buckthorn, and Coast Teatree control has been undertaken at Lanky’s Well, Little Dip CP, Canunda NP and Robe Heritage Agreement. Bluebell Creeper and Gazania control has been undertaken at Lanky’s Well. Bridal Creeper control undertaken at Lanky’s Well, Robe Heritage Agreement, Little Dip CP, and Coorong NP.

  • Liaison and awareness-raising activities undertaken with land managers.

  • Threats to sub-populations identified.

  • Track re-aligned and bollards erected at sub-populations in Little Dip CP to prevent damage to sub-populations by off-road vehicles in 2007.

  • Pollinator for C. richardsiorum identified as the thynnid wasps Phymatothynnus n.sp. nr pygidialis belonging to the Phymatothynnus pygidialis complex (Brown & Vleck 2010).

  • Negotiation for germplasm and mycorrhizal fungi storage conducted.

  • Existing data collated.

  • Development of a relational database commenced, for storage of spatial, monitoring and management data.

3.8 Community engagement


The importance of community support cannot be underestimated in the conservation of C. richardsiorum. Two local groups, the Friends of Little Dip and Butchers Gap Conservation Parks and the Beachport District Development Corporation have made a significant effort to protect this species. Extinction of some sub-populations would have almost certainly taken place without their support. The Natural History Society of South Australia has also undertaken extensive weed control work in potential C. richardsiorum habitat. These works have included identification of new sub-populations, weed control and raising awareness of the significance of this species within the community and government.

Figure 1. Distribution of Caladenia richardsiorum, Little Dip Spider-orchid.


4.0 Caladenia calcicola G.W.Carr (Limestone Spider-orchid)

4.1 Description


Caladenia calcicola is a perennial spider-orchid with a single, lanceolate leaf up to 15 cm long with dense hairs on both laminae and one or sometimes two glossy flowers, up to 40 mm in width (Backhouse & Jeanes 1995). The flowering stem is 10-28 cm in length. Petals and sepals are pale yellow in colour with up to two central maroon stripes. Sepals are up to 9 mm long and have prominent clubs varying in colour from yellow to red. Flowering occurs from mid-September to early November. The plant remains dormant when conditions are unsuitable (Bates & Weber 1990; Backhouse & Jeanes 1995; Bishop 1996; Carr 1986). For a formal description of the species see Carr (1986).

Initial investigations identified a number of plants at Padthaway that bore a strong resemblance to C. calcicola. Further investigation found that the individuals in question were C. reticulata. Caladenia calcicola was previously known to occur in the Mt Burr Range, South Australia; however this sub-population is now extinct and no extant sub-populations are known to exist in South Australia. Caladenia calcicola was also previously included in the C. reticulata complex.


4.2 Conservation Status


Caladenia calcicola is listed as nationally Vulnerable under the Commonwealth EPBC Act, Endangered under the South Australian NPW Act, and Threatened in Victoria under the Flora and Fauna Guarantee Act 1988 (FFG Act).

4.3 Distribution and Population Size


Caladenia calcicola grows in shallow, terra-rossa soil on limestone ridges in south-west Victoria and south-east South Australia. Although now very restricted, it may have been more widespread prior to European settlement. The species has a distribution of approximately 90 km2 and occupies no more than 10 km2 (Figure 2). No suitable vegetation remains in its previous habitat around Mt. Burr Range in South Australia.

The total population of mature plants of C. calcicola in 2007 was 277, consisting of 211 individuals in six naturally occurring sub-populations located in Victoria, and an additional 66 plants in two translocated sub-populations (Table 5).

The sub-populations at a Wildlife Reserve near Portland are found within an area of less than 10 km2. Surveys undertaken between 1989 and 1992 and in 2000 found the sub-populations to be in decline (DNRE 1992). Previously the largest known sub-population nearby on private land was partially destroyed by quarrying between 1980 and 1984 (Carr 1986). A sub-population was discovered in 2006 on the Wildlife Reserve, 100 m from the previously known sub-population. It is believed to be part of the original sub-population.

The sub-population on private land near Dunkeld was first reported in November 1989, when it numbered two individuals (D. Munro pers. comm. 2001).



In October 1994, five flowering plants were located in the Lower Glenelg National Park near Nelson. This number has remained constant over time.

Table 5. Reserved and unreserved sub-populations of Caladenia calcicola.

Location

Manager

No. of individuals

No. of sub-populations

Year

Reserved Sub-populations 

Natural

Lower Glenelg NP, Nelson, Vic

Parks Victoria

5

1

2008

Wildlife Reserve, Portland, Vic

205

4

2007

Re-introduced

Wildlife Reserve, Portland, Vic

Parks Victoria

66

2

2007

Total Reserved 

276

7




Unreserved Sub-populations 

Dunkeld, Vic

Private Property

1

1

2007

Total Unreserved 

1

1





4.4 Habitat


At the Bats Ridge Wildlife Reserve near Portland, C. calcicola occurs in Limestone Ridge Woodland. Dominant species include Manna Gum (Eucalyptus viminalis ssp. cygnetensis), Golden Wattle (Acacia pycnantha), Coast Wattle (Acacia longifolia subsp. sophorae), Sweet Bursaria (Bursaria spinosa) and Coast Beard-heath (Leucopogon parviflorus) (Carr 1986). In the Lower Glenelg National Park at Nelson it occurs in Limestone Woodland dominated by Drooping Sheoak (Allocasuarina verticillata), Swamp Gum (Eucalyptus ovata), Golden Wattle, Myrtle Wattle (Acacia myrtifolia), Common Heath (Epacris impressa) and Common Correa (Correa reflexa). On private land at Dunkeld it occurs in a Grassy Woodland/Hills Herb-rich Woodland/Damp Sands Herb-rich Woodland mosaic dominated by Manna Gum, Silver Banksia (Banksia marginata), and Bracken Fern (Pteridium esculentum).

Habitat critical to the survival of this species includes the area occupied by the sub-populations, and areas for future recruitment of sub-populations. The entire tract of vegetation in which C. calcicola occurs should be considered habitat critical to the survival of the species, including vegetation with the appropriate floristic composition described above. Preventing any further fragmentation of existing vegetation that currently or potentially supports this species, is crucial to its long-term survival.

To maintain a self-sustaining sub-population of C. calcicola it is also vital to conserve the pollinator’s habitat. While the exact habitat requirements of the pollinator, Phymatothynnus near nitidus, are not well understood, it is known that Thynnids feed on a range of flowering plants, particularly from the Myrtaceae and Proteaceae families. It is important for the pollinator population that flowering food plants are available before, during and after the flowering period of C. calcicola, as the pollinators have been observed to be present for a few months before and after the orchid flowering period (C. Bower pers. comm. 2007). Definition of the pollinator habitat requires further investigation.

4.5 Ecology

4.5.1 Mycorrhizae

Mycorrhizal fungi have been isolated from a Victorian sub-population of C. calcicola and plants propagated with the fungi were reintroduced into natural habitat in 2007.
4.5.2 Pollination

Natural pollination of C. calcicola is very low throughout its range. Observations indicated that 5% - 10% of plants were pollinated annually at the Wildlife Reserve sub-population (DNRE 1992). However, in 2007 the natural pollination rate for all sub-populations was less than 5% (A. Pritchard pers. obs. 2007).

In 2006, pollinator baiting was conducted (Bower 2007). The pollinator of C. calcicola was identified as a thynnid wasp, Phymatothynnus near nitidus, by entomologist Dr. G Brown (Bower 2007). Phymatothynnus nr. nitidus was found to pollinate two other closely related orchid species, C. reticulata and C. strigosa (formerly C. australis), during the same trial period (Bower 2007). Further research is needed on the C. reticulata complex and its pollinator, P nr. nitidus, to identify whether the pollinator actually is comprised of separate cryptic species which each only pollinate one species of Caladenia or whether the C. reticulata complex is one biological species (Bower 2007). Phymatothynnus nr. nitidus was found to be scarce around the existing sub-populations of C. calcicola, but locally common throughout the rest of the Wildlife Reserve.


4.6 Threats


Threats common to all species are outlined earlier in this document. Threats relating specifically to this species are:

  • Grazing. Grazing by native and introduced herbivores, including rabbits, kangaroos and emus for all sub-populations. Emus have removed tags and pins at C. calcicola sub-populations and may cause associated damage to individual plants as a result (A. Pritchard pers. obs. 2004).

  • Weed invasion. Bridal Creeper (Asparagus asparagoides), Italian Buckthorn (Rhamnus alaternus), Arum Lilies (Zantedeschia aethiopica) and Hypochaeris sp. pose a problem at the Wildlife Reserve site. South African Weed Orchid (Disa bracteata) poses a potentially high level threat to the Nelson sub-population, given its close proximity to significant outbreaks nearby.

  • Site disturbance. Accidental site damage as a result of off-road activity by vehicles affects the Wildlife Reserve and the Nelson sub-populations and is considered a high risk at all public land sites.

  • Inappropriate burning regimes. Optimal fire regimes for maintaining, or re-creating, the appropriate vegetation age-class and structure have not been determined, however it is recognised that many terrestrial Australian Caladenia species respond favourably to fire events that reduce canopy biomass. In the future the effect of inappropriate burning regimes on the pollinator and the associated mycorrhizal fungi also needs to be considered if self-sustained sub-populations are to be maintained.

  • Illegal collection. Collecting of the species by plant enthusiasts is considered a potential threat at all sites, given the rarity of this species.

  • Reduced pollination rates. Observations in recent years suggest that pollination rates at all sites may be too low to maintain a stable population size.

4.7 Previous Recovery Actions


An ecologist has been employed to plan and implement recovery of C. calcicola since 1994. Conservation measures have been undertaken by DSE, Parks Victoria (PV) and DEWNR. These activities include;

  • Conservation Covenant established at the private property site in Victoria.

  • Control of Italian Buckthorn (Rhamnus alaternus) at Wildlife Reserve, Portland.

  • Management priorities incorporated into the Glenelg Hopkins Catchment Management Authority Regional Catchment Strategy.

  • Information relating to the distribution of the species included in the DSE and PV’s Fire Operation Plans to minimise accidental damage during fire control activities.

  • 66 individuals have been re-introduced at two sites in the Wildlife Reserve at Portland.

  • Monitoring has been undertaken at all public land sites since 1994 and began at the Wildlife Reserve site in 1992. Collected life history data for all sites suggests that all sub-populations are currently in decline.

  • Slide baiting of soils was undertaken in 2004 to extract mycorrhizal fungi, but was unsuccessful. An alternative method undertaken by the Royal Botanic Gardens, Melbourne, of taking a slice of the orchid’s collar was successful in isolating the mycorrhizal fungi. The mycorrhizal fungi are in long-term storage at the Gardens. Preliminary data have indicated that taking a slice of the plant collar has no detrimental effect on future growth and reproductive ability (M. Wright pers. comm. 2007).

  • In-situ conservation program at the Royal Botanic Gardens, Melbourne.

  • Following the discovery that pollination rates were not high enough to sustain the population, hand pollination has been performed at targeted sub-populations to enhance seed set.

  • The results of a pollinator baiting experiment in the Wildlife Reserve (Portland) in 2006 (Bower 2007), indicated the Thynnid pollinator was scarce in the immediate vicinity of known sub-populations, yet locally common along adjacent tracks. Currently the adjacent area is unsuitable for C. calcicola as the vegetation has become very dense, predominantly due to the invasion of Coast Wattle (Acacia longifolia subsp. sophorae) and lack of fire within the Reserve. To achieve natural pollination and create a self-sustaining sub-population of C. calcicola, Bower (2007) suggests potentially reintroducing C. calcicola to the areas of the Reserve with a good pollinator population. The reintroduction site would need to be prepared to create a more open environment suitable for the orchid. It would be possible to create the appropriate vegetation structure by conducting a prescribed burning regime during the dormancy periods of the orchid and pollinator, or by undertaking manual vegetation removal. Both methods will require ongoing management to maintain the habitat in a suitable condition for the orchid and its pollinator.

  • Fencing has been undertaken at the Wildlife Reserve to exclude rabbits and on private land at Dunkeld to exclude stock. A fence has also been erected at Nelson to prevent machinery from creating further damage to the site. Additional plants have also been caged at a number of sites to protect them from both native and exotic herbivores.

  • Mapping and searching of potential habitat has been undertaken by both DSE and DEWNR. Two new sub-populations were located in 2006 by DSE in Victoria and can be attributed to the habitat mapping undertaken.

  • Re-examined taxonomy of the sub-population at Padthaway Conservation Park, South Australia – now considered to be C. reticulata complex.

  • A multi-species recovery team has been set up by DSE for threatened flora in South West Region, Victoria, and a number of meetings with regional stakeholders have taken place to manage the recovery of these species, including C. calcicola.



Figure 2. Current and historic distribution of Caladenia calcicola, Limestone Spider-orchid.

5.0 Pterostylis tenuissima Nicholls (Swamp Greenhood)

5.1 Description


Pterostylis tenuissima is a perennial terrestrial greenhood orchid. When in the non-reproductive stage it appears as a rosette, however, the rosette is absent when in flowering form. The flowering form has up to five stem-sheathing leaves (10-30 mm long) along its flower stem. The stem reaches up to 300 mm in length and supports a single, nodding flower. The modified sepal, known as the hood, is translucent white in colour with pale green stripes ranging in length from 15-20 mm. Lateral sepals are held erect, with long fine tips up to 20 mm rising above the hood. Flowering occurs mainly between October and March but is frequently observed at other times throughout the year. Non-flowering plants form a ground-hugging rosette of three to eight dark green, glossy ovate leaves. Pterostylis tenuissima can remain dormant as an underground tuber when conditions are unsuitable (Bates & Weber 1990; Backhouse & Jeanes 1995; Jessop & Toelken 1986).

5.2 Conservation Status


Pterostylis tenuissima is listed as nationally Vulnerable under the Commonwealth EPBC Act, Vulnerable in South Australia under the NPW Act and Threatened under the Victorian FFG Act.

5.3 Distribution and Population Size


Pterostylis tenuissima is found between Wilsons Promontory National Park in eastern Victoria and West Dairy Range in south-east South Australia (Figure 3). The species is mainly restricted to the coastal plains of south-east South Australia and south-west Victoria, with one sub-population recorded 90 km inland near Poolaijelo in Victoria. Although widespread, the habitat for this species has been significantly depleted, resulting in a significant reduction in numbers across its range. The species is known from 55 sites. Given the historical distribution of suitable habitat across south-east South Australia and south-west Victoria, it is likely that the species was once far more widespread and abundant than it is today. Pterostylis tenuissima is distributed across approximately 1,000 km2 and occupies no more than 10 km2.

The estimated total number of mature plants of P. tenuissima is 17,703, consisting of 57 sub-populations located in Victoria and South Australia (Table 6). The high number of sub-populations reflects the highly fragmented nature of the distribution of this species. Five sub-populations are protected within National Parks in Victoria and one in a Wildlife Reserve near Princetown. Three sub-populations have been recorded at Piccaninnie Ponds Conservation Park, South Australia, including at least one within the recent addition to the park (Pick Swamp). It is likely that this number will increase, following searches of these newly reserved sites. The density of plants at Pick Swamp was reasonably high and as such the total number of plants could be in excess of 1,000. The total number of plants and sub-populations at this site is currently unknown but will be investigated in future years.

Currently 46 of the 57 known sub-populations are found on private property, most of which are subject to agricultural land uses. Only one of these properties is protected by a Conservation Covenant on the land title. In Victoria four sub-populations occur on roadsides managed by local government and one occurs in a council reserve.

Table 6. Reserved and unreserved sub-populations of Pterostylis tenuissima.

Location

Manager

No. of individuals

No. of sub-populations

Year

Reserved sub-populations 

 


Piccaninnie Ponds CP, SA

DEWNR

1,039

3

2004

Discovery Bay Coastal Park, Nelson, Vic

Parks Victoria

24

1

2004

Lower Glenelg NP, Nelson, Vic

22

2

2004

Port Campbell NP, Port Campbell, Vic

<10

1

2004

Serpentine Ck Wildlife Reserve, Princetown, Vic

<50

2

2004

Wilsons Promontory NP, Vic

15

2

2006

Trust for Nature Sanctuary, Naringal East, Vic

Private Property

41

1

2004

Total Reserved

1,201

12




Unreserved sub-populations


Blackfellows Caves, SA

Private Property

53

1

2004

Nene Valley, SA

22

1

2004

West Dairy Range 1, Robe, SA

1,750

2

2004

West Dairy Range 2, Robe, SA

56

1

2004

Brucknell 1, Vic

200

1

2004

Brucknell 2, Vic

420

1

2004

Chappel Vale, Vic

20

1

2004

Curdie Vale 1, Vic

500

2

2004

Curdie Vale 2, Vic

4,000

7

2004

Curdie Vale 3, Vic

Data Deficient

2




Curdie Vale 4, Vic

>4,500

5

2007

Curdie Vale 5, Vic

90

2

2004

Curdie Vale 6, Vic

300

1

2004

Curdies River 1, Vic

200

1

2004

Curdies River 2, Vic

180

1

2004

Curdies River 3, Vic

122

1

2004

Curdies River 4, Vic

70

1

2004

Curdies River 5, Vic

223

1

2004

Curdies River 6, Vic

117

1

2004

Curdies River 7, Vic

1,500

1

2004

Narringal East, Vic

> 200

1

2004

Poolaijello, Vic

200

1

2004

Princetown, Vic

300

1

2004

Red Cap Creek, Vic

24

1

2004

Terang, Vic

7

1

2004

Tyrendarra, Vic

< 50

1

2004

Princetown Recreation Reserve, Princetown, Vic

Corangamite Shire Council

1,000

1

2004

Roadside 1, Lower Heytesbury, Vic

46

1

2004

Roadside 2, Lower Heytesbury

30

1

2004

Roadside, Brucknell, Vic

Moyle Shire Council

300

1

2004

Roadside, Curdie Vale, Vic

22

1

2004

Total Unreserved

16,502

45





5.4 Habitat


Pterostylis tenuissima occurs exclusively in Silky Tea-tree (Leptospermum lanigerum) Scrub, known as Swamp Scrub in Victoria. Habitat critical for the survival of this species is defined as all remaining areas of Silky Tea-tree Scrub.

Silky Tea-tree Scrub occurs on delicate, alkaline soils in swamps and along the edges of rivers and creeks. Seasonal inundation can occur within these communities, however in South Australia these wetlands are predominantly fed by freshwater springs with minor seasonal variation. Co-dominant canopy species often include Scented Paper-bark (Melaleuca squarrosa) and Tree Daisy (Ozothamnus ferrugineus) (Backhouse & Jeanes 1995; Croft & Carpenter 2000).

The extent of Silky Tea-tree Scrub has been heavily depleted through extensive clearance and drainage for agriculture in both South Australia and Victoria. Remnants on private land are often subject to grazing by cattle and sheep. Stock often force their way through the dense understorey, opening up the overstorey and damaging the soil structure. Small sub-populations are found under mature Silky Tea-tree plants only millimetres above the water table. These delicate, waterlogged soils are highly susceptible to pugging. Significant changes in canopy cover can lead to the invasion of more light tolerant species (often exotic pasture species) that can out-compete P. tenuissima. They may also lead to increased water loss from the soil through evaporation (Bachmann 2002). Silky Tea-tree Scrub is adapted to relatively stable environmental conditions and responds very poorly to clearance and stock disturbance.

In Victoria Silky Tea-tree Scrub occurs along the Curdies and Gellibrand Rivers, their associated tributaries, and coastal wetlands in the far south-west of the State, primarily on private land that is used for dairy, beef or sheep production. Currently the largest and most intact remnants occur in the South West coastal region of Victoria. South-west Victoria also contains the only areas of reserved coastal Silky Tea-tree Scrub in Victoria, at Snape Reserve Princetown and Ralph Illiage Trust for Nature Sanctuary.


5.5 Ecology

5.5.1 Mycorrhizae

The fungi that form mycorrhizal relationships with P. tenuissima have not yet been isolated; however the techniques for isolation are well established for similar species. As there is little knowledge available regarding the mycorrhizal associations of this particular species, identification and subsequent mapping of suitable fungi is desirable for its recovery.
5.5.2 Pollination

The pollinator(s) of P. tenuissima have not been identified.

There are no data on the pollination rates for most sites; however field observations indicate that rates are higher in larger sub-populations. Observations have determined that the ratio of flowering plants to non-flowering rosettes is frequently low. Pterostylis tenuissima is able to reproduce vegetatively from underground tubers (A. Pritchard pers. obs. 2005), which may reduce its dependence on sexual reproduction. Consequently asexual reproduction may be an important factor in building population size.


5.6 Threats


Threats common to all species are outlined earlier in this document. Threats relating specifically to this species are:

  • Vegetation clearance and fragmentation: In South Australia the distribution of Silky Tea-tree Scrub has been reduced from 10,740 to 2,380 hectares as a result of extensive drainage, clearance and increasing salinity (Croft et al. 1999; Croft & Carpenter 2000). Leptospermum lanigerum shrubland (Silky Tea-tree Scrub) is rated as regionally Vulnerable in South East Region, South Australia (Croft et al. 1999).

In western Victoria, this community is considered Endangered as only 2,415 of the original 53,649 hectares of this habitat remains (CVRFASC 2000). Native vegetation clearance continues to threaten sub-populations found on private property at Gellibrand Creek and Curdies River. Some remnants along creek lines in Victoria are subject to increased levels of groundwater salinity as a result of vegetation clearance.

  • Grazing: Grazing by livestock at most sites on private property is a major threat and can lead to vegetation degradation, initially along the edges of remnants and ultimately across the entire habitat. The fragile habit of P. tenuissima plants makes them highly susceptible to trampling and grazing.

  • Drainage works: Numerous large wetlands once stretched across the Lower South East Region of South Australia (Bachmann 2002). In 1863, construction of the first of many large drains began at Kingston (South East Wetlands Committee 1984), eventually leading to an extensive drainage system that has converted the majority of wetlands to pasture. Wetland drainage continues to pose a serious threat to these communities, particularly on private land where small remnants are under considerable pressure from adjacent agricultural land. Surface drainage works, combined with extensive vegetation clearance, have resulted in the loss and degradation of large areas of habitat in the Nene Valley and at Blackfellows Cave in South Australia. Ongoing drainage and clearance of P. tenuissima habitat near Blackfellows Caves will likely lead to an extinction of the species at this site in future years. Drainage began in the early 1990’s and resulted in almost complete desiccation of this swamp for the first time during the summer of 2000-01. By then, remaining areas of available water supported only 53 P. tenuissima plants, down from 92. Under the current drainage regime, this sub-population may not survive another dry event.

  • Changes to the hydrology: In recent decades, a drop in the level of the unconfined aquifer in the lower south-east of South Australia has led to a reduction of flow to near-coastal springs. This may be the result of a number of factors, including below average rainfall, an increase in groundwater extraction for irrigated agriculture and a reduced recharge to the watertable, as a result of the establishment of plantation forests and widespread surface drainage (L. Schmidt pers. comm. 2001). Consequently, many springs that previously provided a regular flow of water to Silky Tea-tree swamps throughout the year now have reduced flow during summer, making the habitat unsuitable for the moisture-dependent, summer-flowering P. tenuissima. This threatens some sub-populations at Piccaninnie Ponds CP, and has led to the gradual invasion of Coast Wattle (Acacia longifolia subsp. sophorae). Efforts to reverse the effects of this water loss are ongoing; however extreme caution is required to prevent the inundation of existing sub-populations. Consequently, actions to reinstate the hydrology of the wetlands should take into account this species and its requirements.

  • Weeds: A variety of weed species threaten Swamp Greenhood sub-populations, including Blackberries (Rubus spp.), Buffalo Grass (Stenotaphrum secundatum), Arum Lilies (Zantedeschia aethiopica), New Zealand Mirror-bush (Coprosma repens), Cotoneaster (Cotoneaster symondsii) and various pasture species. At Spring and Whiskey Creeks in Victoria, the long, narrow shape of remnant P. tenuissima habitat results in a higher ratio of edge to core area and an increased susceptibility to external influences such as weed invasion.

  • Erosion: This is particularly a problem at Spring and Whiskey Creeks in Victoria. Plants growing along the water’s edge are vulnerable to advancing erosion, and the potential to be washed away.

  • Site disturbance: Visitor impacts from naturalists and field officers also threaten some sub-populations. Monitoring activities are often time consuming and can lead to damage, particularly of the soft soils of P. tenuissima habitat.

5.7 Previous Recovery Actions


Staff have been employed by DEWNR and DSE since 2000 to plan and manage the recovery of P. tenuissima. Liaison with private landholders has been undertaken both in Victoria and South Australia to locate and protect Silky Tea-tree Scrub.

Through the Silky Tea-tree & Cutting Grass Wetland Rehabilitation Project in South Australia (Bachmann 2002), assistance was provided to landholders to fence remnants on private property. The success of rehabilitation works was also evaluated and additional searches undertaken to locate new sub-populations of threatened flora, including P. tenuissima. Incentives will continue to be available for fencing the remaining patches of P. tenuissima habitat.

Ongoing drainage and damage by stock threatened one sub-population on private land in South Australia until recently, when the property was purchased by DEWNR. This has led to benefits to a range of other rare and threatened species at the site and contributed to the development of a wetland corridor in the Lower South East of South Australia.

Several known P. tenuissima sub-populations on private properties in the Curdies and Gellibrand River systems have been fenced to protect the P. tenuissima sub-populations and the Silky Tea-tree Scrub from grazing.



The following management actions have also been undertaken since 2000:

  • Baseline data collected at all sites, including number of individuals and site description.

  • Collection of demographic life history data at sites in Victoria and South Australia: at two sites in South Australia the reproductive state of individuals has been monitored, and at 15 sites in Victoria the number of flowering and non-flowering plants has been monitored every two to three years.

  • Threats to sub-populations identified, the primary threats have included change in hydrology, weed invasion, and grazing.

  • Recovery strategies to mitigate threats have been developed and implemented at key sub-populations. Mitigation activities include fencing, weed control, hydrological restoration and inclusion in fire planning.

  • Surveys and mapping of Leptospermum lanigerum shrubland to locate additional sub-populations.

  • Collation of data and development of Threatened Orchid Database.

  • A total of 250 ha of land purchased in South Australia to protect P. tenuissima and a range of other threatened flora and fauna.

  • Landholder liaison and subsequent threat abatement at sites on private property in both South Australia and Victoria.

  • Investigations to protect P. tenuissima sub-populations in relation to the reinstatement of hydrology in Piccaninnie Ponds wetland complex in south-east South Australia. Mapping of some of the most vulnerable sub-populations has been undertaken however further work is still required. A weir and levy were installed in 2006 and 2008 respectively and further works are proposed.

  • Control of weeds at priority sites within Curdies River - Gellibrand Management zone.

  • Fencing undertaken on three private land sites in South Australia, protecting four sub-populations.

  • Management priorities incorporated into the GHCMA and CCMA Regional Catchment Strategies.

  • Information relating to the distribution of the species included in both DSE and PV Fire Operation Plans to minimise accidental damage during fire control activities.

  • Victorian Regional Recovery Team coordinated by DSE.

  • South Australian Regional Recovery Team coordinated by DEWNR.



Figure 3. Current and historic distribution of Pterostylis tenuissima, Swamp Greenhood
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