Survey of threatened plant species in South East Queensland biogeographical region queensland cra/rfa steering committee survey of threatened plant species in

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3.31 Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781)

3.31.1 Summary

Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is known from four sites near Tewantin in south east Queensland. It has a distribution range of approximately 5 km with a area of occurrence of approximately 7 km². Two of the populations are on freehold land, and two on state forest land. The total area of occupancy is approximately 2 hectares. The largest known population is on freehold land. Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) occurs in shrubland on rocky hillslopes and in tall open forest on gently inclined slopes or flat terrain on the coastal plain. Potential threats to the survival of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) arise from inappropriate fire regime, weed invasion of the habitat and the lack of secure tenure.

3.31.2 Species description and identification

The genus Prostanthera is placed in the mint family (Lamiaceae). Prostanthera is endemic to Australia where there are approximately 100 species distributed throughout all states.

Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) has not been formally described under the conventions in the International Code of Botanical Nomenclature. The botanical description of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is as follows:
Low, straggling or compact shrub to 1 m high, strongly aromatic; branches glabrous except for a band of hairs between lateral ridges; hairs short, curled and antrorse. Leaves with lamina obovate to more or less spathulate, 5-9 mm long, 4-8 mm wide; apex rounded; base long-attenuate; margins entire; upper surface mid green, lower surface, moderately covered with more or less sessile glands; petiole 1-2 mm long. Flowers axillary, part-inflorescence 1-flowered; bracteoles not persistent, size not known. Calyx 4-4.5 mm long; tube 2-2.5 mm long; upper lobe c. 2 mm long, slightly enlarged in fruit. Corolla 6-7 mm long, bluish. Anthers with appendage 0.5-0.7 mm long. Fruit comprising of 4 rugose mericarps, approximately 1.5 mm long (see Plate 26).
The species belongs in the section Prostanthera. This section of the genus is distinguished in having calyx lobes of unequal length; corollas mauve to blue-purple or white; corolla tube short, broad apically; lower corolla lobe longer and more spreading than the erect upper lobes; fruits enclosed by inward folded lower calyx lobe; and the upper calyx lobe usually recurved.
The affinities of this species are presently uncertain. Examination of Queensland Herbarium material shows that this species closely resembles a recently described species, Prostanthera palustris B.J. Conn, from the Bundjalung N.P. near Evans Head in northern New South Wales. The description of P. palustris clearly indicates that it has non-aromatic leaves and that this is one of the distinguishing features of this species (Conn 1997). Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) appears to differ only from P. palustris in having strongly aromatic leaves. Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) and P. palustris appear to be the same species but this will need to be confirmed. Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is easily distinguished from other Prostanthera species in south east Queensland by its obovate to more or less spathulate leaves.

3.31.3 Current conservation status

Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is presently listed on the schedule of the Queensland Nature Conservation Act 1992 as “vulnerable wildlife”. It is also listed on Schedule 1 Part 2 (vulnerable) of the Commonwealth Endangered Species Protection Act 1992. ANZECC (1993) referred to this species under the name Prostanthera sp. Mt Tinbeerwah (C. Sandercoe C1286) when assigning it a national conservation status of V (vulnerable).

3.31.4 Distribution and abundance

A compilation of Queensland Herbarium records of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is presented in Appendix 1.30. This species was only known from three specimens collected in the proximity of Mt Tinbeerwah, approximately 10 km west of Noosa. Another population was reported to occur on the rocky outcrop on Mt Tinbeerwah but had never been vouchered (Mr G. Thomas pers. comm.). Two of the four known sites are on freehold land and two are on State Forest land. Only three of the four sites have been located by the present survey work. Information on habitat and locality data for the site not visited during the present survey has been supplied from field notes of the original collector (C. Sandercoe pers. comm.).

Detailed information of these populations are presented in Appendix 2.9. A summary of population information is presented in Table 3.31.1. The distribution of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) has a range of approximately 5 km and encompasses an area of occurrence of approximately 7 km². The total population is estimated to be less than 2000 individuals.
Lot 183: This occurrence was originally thought to be within Tewantin State Forest. The stand is on the waning lower slope of Mt Tinbeerwah, below the southern cliff face. The population of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) was only estimated visually because the ground layer was very dense and the plants of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) were interwoven in the vegetation. It was apparent in the field that an accurate count could be achieved only by tracing all stems back to their sources. Apart from being very time-consuming, it would have caused the destruction of the plants and the surrounding vegetation.
Illoura Place: This occurrence is situated near the western boundary of the freehold block. A large portion of the block has been cleared in the past but has been allowed to regenerate naturally. Where Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) occurs, it appears that the land has only been partially cleared. The freehold property to the west has been heavily grazed.
Mt Tinbeerwah: This occurrence is within Tewantin State Forest (SF 959 Fty 1295). The population is accessible from the walkway from the carpark to the summit of the mountain. The stand of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) extends over an area of approximately 200 m by 50 m . At this site Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) grows in the shallow pockets of soil that are scattered over the rock face. There are no commercial timber values in the vicinity of the population. The area is presently managed jointly by Department of Natural Resources and the Department of Primary Industries, Forestry.
Table 3.31.1. Estimated Abundance, area of occupancy and land tenure for Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) sites in Queensland surveyed in 1997.

Site	Date sampled	Population size	Area occupied (m²)	Land tenure
Mt Tinbeerwah (Tewantin SF)	7 Oct 1997	52 mature 8 juvenile	10000	SF
Lot 1/RP205063 (Illoura Place)	27 Oct 1997	21 mature	30	Freehold
Lot 183/MCH947	27 Oct 1997	500-1000 mature	10000	Freehold
Tewantin SF (Sandercoe C1286)	4 Dec 1997	unknown	unknown	SF
Total		500-1000	+20030

3.31.5 Habitat

The habitat data for the four sites are set out in Appendix 2.9.

Lot 183: The site is situated on the lower southern slope of Mt Tinbeerwah. The soil is a black clay loam with a surface pH 4.2. The geology is mapped as Myrtle Creek Sandstone. The vegetation structure is a layered very tall open forest. The common overstorey trees are Syncarpia glomulifera subsp. glomulifera, Corymbia intermedia and Eucalyptus pilularis. Common mid-stratum species are Allocasuarina littoralis, Synoum glandulosum and Leptospermum polygalifolium. The ground layer is dense. The common species included Schoenus melanostachys, Gahnia clarkei, Dianella longifolia, Smilax australis, Prostanthera sp. (Tinbeerwah P.R.Sharpe 4781) and Lomandra hystrix.
Mt Tinbeerwah (Plate 28): The site occurs on the steep rocky platform. The soils are shallow reddish black loam with a high organic content and pH 4.2. The geology is mapped as Tertiary, trachyte, comendite, trachyrhyolite, mangerite, syenite. The vegetation structure is an open shrubland. Common species included Leptospermum microcarpum, Acacia hubbardiana, Allocasuarina littoralis, Commersonia sp. (Mt Tinbeerwah G.P.Guymer 1786), Goodenia rotundifolia, Lepidosperma laterale, Aristida benthamii var. benthamii, Dianella caerulea var. vannata, Digitaria parviflora, Eriostemon difformis subsp. smithianus. A number of exotic weed species were observed around the lookout on the summit and on the disturbed soil at the edge of the walkway from the carpark. These included: Bidens pilosa, Brachiaria decumbens, Conyza sumatrensis, Eragrostis mexicana subsp. mexicana, Ipomoea batatas, Lantana camara, Melinis minutiflora and Melinis repens.
Illoura Place (Plate 29): The site is situated on the gently undulating coastal plain. The soil is a dark reddish brown loam with a surface pH 4.5. The geology is mapped as Quaternary alluvium. The vegetation at the site has been partially cleared. The vegetation structure is a tall open forest. The common overstorey trees are Syncarpia glomulifera subsp. glomulifera, Corymbia intermedia and Eucalyptus umbra. The understorey is mid-dense with the common species including Acacia aulacocarpa, Alphitonia excelsa, Elaeocarpus obovatus, Petalostigma triloculare, Melaleuca nodosa, Dianella caerulea var. vannata, Entolasia stricta, Hibbertia aspera, Pultenaea myrtoides, Pultenaea retusa, Zieria minutiflora, Melaleuca quinquenervia and Lomandra longifolia.
Tewantin SF (Sandercoe 1286): The site is situated on a flat sandy area near a drainage line in the eastern end of the State Forest near Harry Spring Environmental Park. The vegetation structure is a tall open forest. The common overstorey trees are Eucalyptus resinifera, Syncarpia glomulifera and Corymbia intermedia.

3.31.6 Life history and ecology

There have been no studies into the biology or autecology of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781). Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is not known to be in cultivation but a number of Prostanthera species have been cultivated as common garden plants for many years (Wrigley and Fagg 1996). Prostanthera species are readily propagated from cuttings.

Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is a herbaceous shrub with an unknown life span. The main method of reproduction is by sexually produced seeds. However, Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) has been observed to produce roots from branch nodes where the branches come in contact with the soil surface (Plate 27) Observations of the population on Mt Tinbeerwah indicate that the plants are fire-sensitive. The species does not appear to have a lignotuber or similar root structures so regeneration after fire relies on the successful germination of seed. However, Prostanthera palustris (Prostanthera sp. 7) in New South Wales was observed to apparently resprout from basal stem buds, after a high-intensity fire (Quinn et al. 1995).
Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) has been recorded flowering in January, April and November. The most common pollinators of section Prostanthera have been reported to be bees (Conn 1984). Fruits develop and mature soon after flowering. The fruit comprises 4 (1-seeded) nutlets which fall from the fruit after maturity. There is no information about seed viability and germination.

3.31.7 Threats

In the light of the available information, current or potential threats to the continued survival of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) in the wild are an inappropriate fire regime, weed invasion of the habitat and the lack of secure tenure for the largest known populations.

Two of the four known sites are on freehold land where changes of land management may lead to the destruction of the populations. The lack of secure land tenure for these two sites is a direct threat to the long term viability of the species at those sites and possibly to the long term viability of the species as a whole in south east Queensland.
The Mt Tinbeerwah population is on the rock outcrop north of the walkway from the carpark to the summit. Presently the population is free of exotic weed species. However there are several exotic species on the shallow soils along the edge of the walkway and around the lookout at the summit. There is a potential for these exotic plant species to encroach on the habitat of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781). The impact that such a weed species invasion would have on Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is uncertain. However, it can be assumed that weeds would change the vegetation structure and lead to increased competition for available habitat resources. Therefore a potential threat to Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is the invasion of weed species into the habitat.
Anecdotal evidence suggest that plants of Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) are fire-sensitive and are not capable of regenerating from underground organs. The continued existence of the species in the wild after a fire would require the regeneration of the species from seed (obligate seeder). If fires were at a frequency that did not allow the replenishment of adequate seed in the seedbank for future recruitment events then the population would decline and the species would be eliminated from the area. This is a potential threat at all sites. However, the habitat at Mt Tinbeerwah may provide some degree of protection from frequent burning in that the rocky outcrops and pavements buffer plants from fires.

3.31.8 Management, Research and Conservation Measures

One of the first steps towards the protection of this species in the wild should be to protect the existing populations and their habitat. The majority of the population is on two lots of freehold land. Liaison with land owners and local authorities are required to make them aware of the presence of the species and the importance of protecting the populations. Discussions should be undertaken with the land holders in regard to protecting the areas with Conservation Agreements under the Queensland Nature Conservation Act 1992. The acquisition of the areas appears unwarranted because of their small size and lack of other biodiversity benefits.

Targeting the lack of autecological data is another priority that should be undertaken for Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781). Research should focus on providing quantitative data on fire ecology, reproduction biology and population dynamics of the species. Such information is crucial for rational management decisions to be made in the future.
The spread of weeds and the condition of habitat on the rock face at Mt Tinbeerwah should be monitored.
Further surveys should be undertaken with the State Forest areas, especially to relocate the State Forest site that was not located in the current survey.
Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) assessed against the IUCN (1994) criteria for threatened wildlife falls into the category of Endangered, ie. is facing a high risk of extinction in the wild in the near future, as defined by criteria B.1, 2.b&e. Extent of occurrence estimated to be less than 5000 km² or area of occupancy estimated to be less than 500 km², and estimates indicating: known to exist at no more than five locations; and continuing decline inferred in area of occupancy and number of mature individuals. On this assessment the present status of Vulnerable for Prostanthera sp. (Mt Tinbeerwah P.R.Sharpe 4781) is considered inappropriate and should be updated to Endangered.

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