Biodiversity

Species Profile and Threats Database


For information to assist proponents in referral, environmental assessments and compliance issues, refer to the Policy Statements and Guidelines (where available), the Conservation Advice (where available) or the Listing Advice (where available).
 
In addition, proponents and land managers should refer to the Recovery Plan (where available) or the Conservation Advice (where available) for recovery, mitigation and conservation information.

EPBC Act Listing Status Listed as Endangered as Sagina diemensis
Listing and Conservation Advices Commonwealth Conservation Advice on Sagina diemensis (Threatened Species Scientific Committee, 2008adf) [Conservation Advice].
 
Commonwealth Listing Advice on Sagina diemensis (Threatened Species Scientific Committee (TSSC), 2008ads) [Listing Advice].
 
Recovery Plan Decision Recovery Plan required, this species had a recovery plan in force at the time the legislation provided for the Minister to decide whether or not to have a recovery plan (19/2/2007).
 
Adopted/Made Recovery Plans Flora Recovery Plan: Alpine Karst Flora: Oreoporanthera petalifera and Sagina diemensis 2006–2010 (Threatened Species Section (TSS), 2006d) [Recovery Plan] as Sagina diemensis.
 
Federal Register of
    Legislative Instruments
Declaration under s178, s181, and s183 of the Environment Protection and Biodiversity Conservation Act 1999 - List of threatened species, List of threatened ecological communities and List of threatening processes (Commonwealth of Australia, 2000) [Legislative Instrument] as Sagina diemensis.
 
Inclusion of species in the list of threatened species under section 178 of the Environment Protection and Biodiversity Conservation Act 1999 (05/10/2001) (Commonwealth of Australia, 2001c) [Legislative Instrument] as Sagina diemensis.
 
Inclusion of species in the list of threatened species under section 178 of the Environment Protection and Biodiversity Conservation Act 1999 (62) (14/11/2008) (Commonwealth of Australia, 2008n) [Legislative Instrument] as Sagina diemensis.
 
State Government
    Documents and Websites
TAS:Threatened Species Notesheet - Sagina diemensis (Tasmanian Department of Primary Industries, Parks, Water and Environment (Tas. DPIPWE), 2009e) [Information Sheet].
TAS:Sagina diemensis (Pearlwort): Species Management Profile for Tasmania's Threatened Species Link (Threatened Species Section (TSS), 2014dr) [State Action Plan].
State Listing Status
TAS: Listed as Endangered (Threatened Species Protection Act 1995 (Tasmania): September 2012 list) as Sagina diemensis
Scientific name Sagina diemensis [64974]
Family Caryophyllaceae:Caryophyllales:Magnoliopsida:Magnoliophyta:Plantae
Species author L.G.Adams
Infraspecies author  
Reference L.G. Adams (1996), Muelleria 9: 64, fig. 1a-e
Other names Sagina sp. 1 (Mt. Anne) [23963]
Sagina sp. Mt Anne (A.M.Buchanan 5115) [56764]
Sagina sp. (A.M. Buchanan 5115; Mt Anne) [67308]
Distribution map Species Distribution Map

This is an indicative distribution map of the present distribution of the species based on best available knowledge. See map caveat for more information.

Other illustrations Google Images

Scientific name: Sagina diemensis

Common name: Pearlwort

This species is conventionally accepted (Buchanan 2005).

Pearlwort is a cushion-forming perennial herb in the Caryophyllaceae family. The species is usually covered in small hairs with glandular tips, has small linear leaves, and small white flowers that occur singly near the ends of its branches.

The stems of the Pearlwort are flexible, stoloniferous and are up to 10 cm long. The leaves are sessile (without a stalk), linear, 2–25 mm long and 0.2–0.5 mm wide. The leaves usually have narrow scarious (dry and transparent) margins, and a pointed tip that may be short and sharp (TSS 2005). The flowers have 4 petals and 4 sepals (4-merous). The stalk of the flower is erect and 6–12 mm long. The sepals are oblong to elliptic, with a pouched base, 2–2.5 mm long. The scarious margins are often purple-tinged and are more-or-less pressed closely to the ripe fruit. The petals are ovate to suborbicular, white and 2.5–3.5 mm long. The flower has four or eight stamens and four styles. The fruit is an oval shaped capsule 2.5–2.75 mm long and contains numerous dark reddish-brown kidney shaped seeds (Adams 1996b; TSS 2005).

Pearlwort is endemic to southwestern Tasmania (Adams 1996b). It is known only from the immediate vicinity of Mt Anne and headwaters of the Weld River in Southwest National Park, which is part of the Tasmanian Wilderness World Heritage Area. The linear range of the species is 9 km (TSS 2006d).

The extent of occurrence of the Pearlwort is approximately 5 km². This estimate was based on the minimum convex polygon encompassing the two known subpopulations (Table 1) (TSS 2006d).

The area of occupancy of this species is estimated be 0.001 km². This estimate was based on an estimate of the summed areas occupied by each of the two subpopulations (Table 1) (TSS 2006d).

The Pearlwort occurs in two locations that represent the two known disjunct subpopulations. The Weld River Arch subpopulation occupies a very small area (Table 1) and is considered vulnerable to a single threatening event (such as trampling by bushwalkers). The Mt Anne subpopulation consists of plants spread over a wider area. A single threatening event capable of rapidly affecting all individuals within this subpopulation is considered less likely (TSS 2006d).

TABLE 1. Pearlwort in Tasmania

  Subpopulations Year last (first) seen Area Occupy (ha) Number of mature plants Specific Threats
1 North East Ridge, Mt Anne 2005
(1982)
< 0.1 24 Climate change; fire; trampling; stochastic risk
2 Weld River 2005
(1988)
0.0001 c. 10 Trampling; stochastic risk
(TSS 2006d)

A number of targeted searches for Pearlwort have been undertaken in Tasmania's southwest since the taxon was recognised in 1984 (Gilfedder 1989), the focus being limestone or dolomite outcrops at altitudes above 600 m (such as North East Ridge of Mt Anne, Mt Ronald Cross, Tim Shea, Mt Gell and Mt Bobs). Department of Primary Industries, Water and Environment (DPIWE) personnel conducted detailed extension surveys of the species' type locality at North East Ridge of Mt Anne in 2005, and also a known site along the Weld River (Balmer & Lambourne 2005; TSS 2006d).

Past survey efforts for the species have been limited by the remoteness and restricted nature of potential dolomite habitat in Tasmania's south-west, as well as the diminutive nature of the species. About half the species' suitable habitat at Mt Anne remains to be surveyed, while several areas of potential habit outside the species' known extent of occurrence have yet to be surveyed (Balmer & Lambourne 2005). The likelihood of additional subpopulations being found is considered to be reasonable, given a well-resourced and targeted survey effort (TSS 2006d). The estimates of population size and area of occupancy should thus be considered to be conservative estimates.

DPIWE surveys in 2005 of about half the available habitat at Mt Anne recorded 24 mature plants over a linear distance of 1 km. Ten mature plants and approximately 90 immature plants were recorded from two sites about 10 m apart at the Weld River (Balmer & Lambourne 2005; TSS 2006d).

Based on the area of unsurveyed suitable habitat at Mt Anne, the total number of mature individuals at that site alone is likely to be at least 50–100 (TSS 2006d).

The species occurs in two subpopulations, one on the North East Ridge of Mt Anne, the other approximately 8 km to the north at the Weld River. Both subpopulations are within the Southwest National Park, part of the Tasmanian Wilderness World Heritage Area (TSS 2006d).

All populations of Pearlwort are considered necessary for its long-term survival.

The known Pearlwort population occurs within the 605 000 ha Southwest National Park, which is part of the Tasmanian Wilderness World Heritage Area (Tas PWS 1999). Past management for the species has consisted of extension surveys and the establishment of monitoring sites. Proposed activities within the Park are subject to the Tasmanian Reserve Management Code of Practice (Tas PWS et al. 2003).

Pearlwort has been recorded from cracks and crevices on exposed dolomite outcrops within subalpine shrublands (Adams 1996b), and also on sparsely vegetated dolomite ledges close to rivers (Balmer & Lambourne 2005). The altitude range of recorded sites is 340–1050 m above sea level (asl) and the annual rainfall is approximately 1750 mm (TSS 2006d).
At the Mt Anne site Pearlwort grows within cracks and crevices in exposed dolomite outcrops, along with species such as Austrodanthonia diemenica, Oreomyrrhis gunnii and Oreoporanthera petalifera (Adams 1996b). The species grows in shallow well-drained soils derived from solution pockets in the dolomite; soils are stony, medium to fine grained, light-grey clayey sand with organic fragments, and are slightly to moderately alkaline (pH 7.4) (TSS n.d., unpubl. data). The recorded altitude range is 970–1050 m. The surrounding low subalpine shrubberies contain species such as Agastachys odorata, Lomatia polymorpha, Persoonia gunnii, Richea scoparia, Richea sprengelioides, Tasmannia lanceolata and the Liliaceous Astelia alpina (Pineapple Grass) (TSS 2006d).

At Weld River, Pearlwort has been recorded from sparsely vegetated dolomite rock ledges above the flood zone. Associated species include Galium australe, Senecio leptocarpus, Australina pusilla, Carex brevifolius, Cardamine sp. and Poa sp. (Balmer & Lambourne 2005). The soils are only a few millimetres thick and nearby slopes are densely vegetated with thick carpets of mosses, ferns and rainforest. The altitude is 340 m asl (TSS 2006d).
Associated EPBC-listed species include the Vulnerable herb Oreoporanthera petalifera (at Mt Anne).

Plants at the Mt Anne subpopulation grow on dolomite outcrops in close proximity to Athrotaxis selaginoides (King Billy pine) subalpine scrub. This community is listed as threatened in schedule 3a of the Tasmanian Nature Conservation Amendment (Threatened Native Vegetation Communities) Bill 2005 tabled in the Tasmanian Parliament in December 2005. The ecological community is not listed under the EPBC Act (R. Schahinger 2005, pers. comm.).

Pearlwort has been observed in flower in December and January (Balmer & Lambourne 2005; TSS n.d., unpubl. data). The species is stoloniferous (produces runners) (Adams 1996b). Seedlings have been observed, though the requirements for recruitment are unknown. The ability of the species to re-establish after fire is unknown although it is likely that the Pearlwort is fire-sensitive (Gilfedder 1989). There is no information on pollinators for this species.

Pearlwort is readily distinguished from other Sagina species by its persistent basal leaf-rosette, its usually strongly glandular-hairy foliage and inflorescence, the saccate base of the sepals, and the relatively conspicuous white corolla (Adams 1996b).

Surveys should be conducted during the species' flowering period, December–February, focusing on dolomite outcrops in Tasmania's southwest.

Climate Change
The impact of the changing global climate, with a trend towards warmer conditions in Tasmania, potentially threatens the survival of a species such as Pearlwort that is currently growing near the apparent upper limit of its temperature range at Mt Anne. The threat of wildfire to the species' subalpine habitat is also likely to be significantly increased (Tas PWS 2004).

Fire
Gilfedder (1989) considered fire to be a potential threat to the plant communities in the species' stronghold, the North East Ridge of Mt Anne, and opined that the apparent absence of the species from other areas of high altitude karst (such as Tim Shea and Mt Ronald Cross) may have been the result of fire. Pearlwort is likely to be sensitive to fire, having evolved in a relatively fire-free environment, though its occurrence in rocky fire-protected microsites means that a reasonable proportion of plants on the North East Ridge of Mt Anne would be expected to survive any wildfire.

Trampling
The North East Ridge of Mt Anne is characterised by extensive limestone sinkholes, and is visited regularly by cavers and bushwalkers. A route has been marked along the complete length of the ridge, potentially threatening plants growing in those sections of the track where it follows the rocky crest of the dolomite ridge. The species' long-term existence at the site is unlikely to be threatened by trampling due to the species' location in a variety of habitats (Gilfedder 1989). DPIWE personnel found the impact of trampling at Mt Anne to be low to negligible in January 2005, though some concerns were raised as to the likely impact of any future increase in visitation levels (TSS n.d., unpubl. data). The Weld River subpopulation is confined to two small patches 10 m apart that are both subject to walker trampling. The very low visitation rates to the area mean that the species' chances of survival are high, as evidenced by the persistence of the subpopulation since its discovery in 1988 (Balmer & Lambourne 2005).

Stochastic Risk
The species' localised distribution, particularly at the Weld River site, exposes it to local extinctions due to unforeseen human activities or stochastic events.

The Threatened Species Scientific Committee (2008ads) recommends the following local and regional priority recovery and threat abatement actions:

  • Protect areas of native vegetation, which contain populations of the species or which could support populations in the future.
  • Develop and implement a suitable fire management strategy for Pearlwort.
  • Undertake appropriate seed and germplasm collection and storage.
  • Undertake survey work in suitable habitat or potential habitat to locate any additional populations.

    Specific recovery objectives identified for the species in the Flora Recovery Plan: Alpine Karst Flora: Oreoporanthera petalifera and Sagina diemensis 2006–2010 (TSS 2006d) are to:

    • Verify that the known population is extant, and conduct a census.
    • Determine the effect of trampling on the population size, and if necessary protect the population.
    • Monitor plants to better understand the species' population dynamics and threats, habitat management and seedling recruitment.
    • Survey for new populations.

    Monitoring and ecology
    Permanent plots were established by DPIWE personnel at several sites in January and March 2005 to monitor the species' population dynamics.

    Extension surveys
    DPIWE personnel have undertaken surveys of the known Weld River site and adjacent areas, and about half the potential habitat at Mt Anne (in January and March 2005). Further surveys are required at Mt Anne and also areas of potential habitat outside the species' known extent of occurrence, such as Lake Timk (Mt Anne area), Mt Riveaux/Picton and Styx River karst areas (Balmer & Lambourne 2005).

    Fire management
    The Southwest National Park is maintained as a fuel-stove only area. Prescribed burning within the Park by the Tasmanian Parks and Wildlife Service is designed to prevent the occurrence of large-scale wildfires, thereby protecting fire-sensitive assets such as the subalpine karst communities supporting Pearlwort (Tas PWS 2004). The prescribed conditions under which fuel reduction burning may be undertaken in areas adjacent to Mt Anne are such that there is a negligible risk of any fire escape spreading to the species' habitat (Tas PWS 2004).

    Ex situ holdings
    The stochastic risk due to the localised distribution of the species means that the possibility of ex situ holdings should be investigated. Seed should be collected and stored as part of the Millennium Seed Bank project being conducted under the auspices of the Royal Botanic Gardens Kew (joint partners in Tasmania include the Royal Tasmanian Botanical Gardens, DPIWE, and the Tasmanian Herbarium).

    Future Management of Pearlwort, at least over the next five years, will be dependent upon the adoption and implementation of the Flora Recovery Plan: Alpine Karst Flora: Oreoporanthera petalifera and Sagina diemensis 2006-2010 (TSS 2006d).

  • The Flora Recovery Plan: Alpine Karst Flora: Oreoporanthera petalifera and Sagina diemensis 2006–2010 provides some brief information on the biology and management plans for Pearlwort (TSS 2006d).

    The following table lists known and perceived threats to this species. Threats are based on the International Union for Conservation of Nature and Natural Resources (IUCN) threat classification version 1.1.

    Threat Class Threatening Species References
    Climate Change and Severe Weather:Climate Change and Severe Weather:Climate change altering atmosphere/hydrosphere temperatures, rainfall patterns and/or frequency of severe weather events Commonwealth Listing Advice on Sagina diemensis (Threatened Species Scientific Committee (TSSC), 2008ads) [Listing Advice].
    Ecosystem/Community Stresses:Indirect Ecosystem Effects:Restricted geographical distribution (area of occupancy and extent of occurrence) Commonwealth Listing Advice on Sagina diemensis (Pearlwort) (Threatened Species Scientific Committee, 2001bo) [Listing Advice].
    Human Intrusions and Disturbance:Recreational Activities:Soil disturbance and/or trampling due to bushwalking Commonwealth Listing Advice on Sagina diemensis (Pearlwort) (Threatened Species Scientific Committee, 2001bo) [Listing Advice].
    Commonwealth Listing Advice on Sagina diemensis (Threatened Species Scientific Committee (TSSC), 2008ads) [Listing Advice].
    Natural System Modifications:Fire and Fire Suppression:Inappropriate and/or changed fire regimes (frequency, timing, intensity) Commonwealth Listing Advice on Sagina diemensis (Threatened Species Scientific Committee (TSSC), 2008ads) [Listing Advice].
    Species Stresses:Indirect Species Effects:Low numbers of individuals Two new endemic species of Sagina L. (Caryophyllaceae) from Australia. Muelleria. 9. (Adams, L.G., 1996b) [Journal].
    Commonwealth Listing Advice on Sagina diemensis (Pearlwort) (Threatened Species Scientific Committee, 2001bo) [Listing Advice].

    Adams, L.G. (1996b). Two new endemic species of Sagina L. (Caryophyllaceae) from Australia. Muelleria. 9.

    Balmer, J. & M. Lambourne (2005). Sagina diemensis population report for Weld River Arch. Unpublished report, Biodiversity Conservation Branch, Department of Primary Industries, Water and Environment, Hobart.

    Buchanan, A.M. (2005). A Census of the Vascular Plants of Tasmania & Index to the Students Flora of Tasmania. Fourth Edition. Tasmanian Herbarium Occasional Publication No. 7. Hobart, Tasmania: Tasmanian Museum and Art Gallery.

    Gilfedder, L. (1989). Five rare Southwest Tasmanian Endemic Plant Species. Unpublished report to the World Wildlife Fund, Hobart.

    Schahinger R. (2005). Personal communication.

    Tasmania Parks and Wildlife Service (Tas PWS) (2004). Prescribed burning in the Tasmanian Wilderness World Heritage Area. Fire Management Section, Tasmania Parks & Wildlife Service, Department of Tourism, Parks, Heritage and the Arts, Hobart, Tasmania.

    Tasmanian Parks and Wildlife Service (Tas PWS) (1999). Tasmanian Wilderness World Heritage Management Plan. [Online]. Hobart, Tasmania. Available from: http://www.parks.tas.gov.au/publications/tech/whaplan/all.pdf.

    Tasmanian Parks and Wildlife Service (Tas. PWS), Forestry Tasmania & Department of Primary Industries, Water and Environment (2003). Tasmanian Reserve Management Code of Practice. Hobart: Department of Tourism, Parks, Heritage and the Arts.

    Threatened Species Section (TSS) (2005). Sagina diemensis: Threatened Flora of Tasmania. [Online]. Hobart: Department of Primary Industries, Water and Environment. Available from: http://www.dpiw.tas.gov.au/inter.nsf/Attachments/SSKA-76P2C2/$FILE/Sagina%20diemensis.pdf.

    Threatened Species Section (TSS) (2006d). Flora Recovery Plan: Alpine Karst Flora: Oreoporanthera petalifera and Sagina diemensis 2006–2010. [Online]. Hobart, Tasmania: Department of Primary Industries and Water. Available from: http://www.environment.gov.au/biodiversity/threatened/publications/s-diemensis-o-petalifera.html.

    Threatened Species Section (TSS) (no date). Unpublished data held by the Threatened Species Section. Tasmanian Department of Primary Industries, Water and Environment (DPIWE), Hobart.

    EPBC Act email updates can be received via the Communities for Communities newsletter and the EPBC Act newsletter.

    This database is designed to provide statutory, biological and ecological information on species and ecological communities, migratory species, marine species, and species and species products subject to international trade and commercial use protected under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act). It has been compiled from a range of sources including listing advice, recovery plans, published literature and individual experts. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. Individuals and organisations should consider all the available information, including that available from other sources, in deciding whether there is a need to make a referral or apply for a permit or exemption under the EPBC Act.

    Citation: Department of the Environment (2014). Sagina diemensis in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Tue, 23 Sep 2014 04:58:21 +1000.