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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3.32 rhodamnia sp. (calliope N. gibson 1335)

3.32.1 Summary

Rhodamnia sp. (Calliope N. Gibson 1335) is known only from SF 583, 45 km S of Gladstone. A total of 19 plants are known in the wild spread over approximately 60 hectares. It grows in a simple microphyll/notophyll vineforest on hillcrests and moderately to very steeply inclined hillslopes with a southerly to easterly aspect and between 200 to 420 m above sea level. The soils are well drained, dark reddish brown loams with an acidic reaction. The species is currently not represented within a secure conservation reserve anywhere in the state. Rhodamnia sp. (Calliope N. Gibson 1335) is considered at risk due to its low known population size and exposure to continued threats associated with fire and the encroachment of lantana into its habitat.

3.32.2 Species description and identification

The genus Rhodamnia is placed in the family Myrtaceae. Rhodamnia occurs from southern China, Burma to Australia and New Caledonia with approximately 28 species (Scott 1979, Mabberley 1997). The genus is represented in Australia by 13 species which are distributed along the east coast.

Rhodamnia sp. (Calliope N. Gibson 1335) has not been formally described but has been recognised as a distinct taxon since 1995. The botanical description of Rhodamnia sp. (Calliope N. Gibson 1335) is as follows:
Erect tree to 8 m high; bark light grey to grey, scaly and shallowly furrowed. Young branches rounded, not winged, glabrous or sparsely sericeous but soon becoming glabrous. Leaves mostly concentrated near branch tips, decussate, opposite, strongly discolorous; petioles 2-4 mm long, channelled on upper surface; lamina narrowly elliptic or rarely obovate, sometimes slightly falcate, 20-70(-85) mm long, (3-)5-12(-15) mm side, cuneate at base, obtuse or broadly acute at apex; margin flat; upper surface sparsely sericeous becoming glabrous with age; lower surface very densely shortly tomentose; intramarginal veins prominent on both surfaces. Flowers in clusters of 2-7 on short axillary shoots; peduncle 1.5 mm long; bracteoles 2, ovate, c. 0.5 mm long, tip not exceeding base of sepal lobes. Hypanthium obconic, sparsely short sericeous. Sepals 4, persistent, fused at base, broadly rounded, 0.3-0.5 mm long, sparsely short sericeous. Petals 4, yellowish-white, widely ovate, c. 2.5 mm long, c. 3 mm wide, glabrous but slightly ciliate on margins. Stamens numerous, multiseriate, excluded; filaments 2-3 mm long; staminal disk glabrous. Style c. 5 mm long, glabrous. Fruit a soft berry, subglobose, 3-4 mm long, 4-5 mm diameter, glabrous or nearly so, yellowish red, 2-4-seeded (Snow and Guymer in press, J. Brushe pers. comm.) (see Plates 30, 31, & 32).
Rhodamnia sp. (Calliope N. Gibson 1335) can be distinguished from other Rhodamnia species in south east Queensland by having 2-7 flowers in short-shooted axillary fascicles, narrowly elliptic leaves and primary lateral veins mostly less than 2 mm from the leaf margin.

3.32.3 Current conservation status

Rhodamnia sp. (Calliope N. Gibson 1335) is presently not listed on the schedule of the Queensland Nature Conservation Act 1992. It is not currently assigned a national conservation status or listed on the Commonwealth Endangered Species Protection Act 1992. However its inclusion on the Queensland Schedule of threatened wildlife as ‘Endangered’ is currently pending. It is to be added to the schedule because it has a very restricted distribution, is not in any formal conservation reserve and is threatened by weed invasion and fires encroaching into its habitat.

3.32.4 Distribution and abundance

A compilation of Queensland Herbarium records of Rhodamnia sp. (Calliope N. Gibson 1335) is presented in Appendix 1.31. All six specimens come from a single locality (and possibly from a single individual) in SF 583 (Fty 1595), approximately 45 km south of Gladstone. An area of approximately 1 hectare had been previously searched within the vicinity of the known individual revealing a total of 3 individuals (one mature and 2 juveniles) within this area. The present study examined the southern and northern slopes below the known locality. No other likely habitats were examined during this present study. Another vineforest along Koolkooroom Creek approximately 20 km south of the present site has been briefly examined but Rhodamnia sp. (Calliope N. Gibson 1335) was not observed to be present (P.I. Forster pers. comm.).

The total population of Rhodamnia sp. (Calliope N. Gibson 1335) was found to be 19 individuals. Another 16 individuals of Rhodamnia sp. (Calliope N. Gibson 1335) were recorded at 5 sites on 2 ridges within the state forest. Information on these populations is presented in Appendix 2.10. The distribution of Rhodamnia sp. (Calliope N. Gibson 1335) has a range of approximately 1 km and encompasses an area of occurrence of approximately 60 hectares. All sites are south of the original site. The largest stand consisted of 7 plants. Other stands consisted of 4, 3 and 2 solitary individuals. A total area of occupancy is estimated to be 3500 m².
The individuals of Rhodamnia sp. (Calliope N. Gibson 1335) observed were all mature plants 2-8 m high and generally healthy except for one individual at site 3. The latter plant consisted of a single young shoot arising from the base of a tree trunk that appeared to have recently died. No seedlings of Rhodamnia sp. (Calliope N. Gibson 1335) were observed.

3.32.5 Habitat

The sites are situated in mountainous terrain on hillcrests and moderate to very steeply inclined hillslopes mostly with a southerly to easterly aspect and at elevations between 200 and 420 m above sea level. The soils are well drained, dark reddish brown loams with a pH 6.2-6.8. The geology is mapped as Muncon Volcanics: intermediate and basic lava, tuff agglomerate, siltstone, lithic arenite, conglomerate, mudstone.

The vegetation in this community is somewhat intermediate between a simple microphyll/notophyll vine forest with Araucaria emergents and semi-evergreen microphyll vine thicket (Plate 34). The common canopy species are Backhousia kingii, Choricarpia subargentea, Barklya syringifolia and Archidendropsis thozetiana. Other common floristic elements observed around the Rhodamnia sites included Diospyros geminata, Tarenna sp. (Ka Ka Mundi N.P. W.J.McDonald+ 5360), Notelaea microcarpa, Carissa ovata, Lantana camara*, Ancistrachne uncinulata, Phyllanthus pusillifolius, Croton acronychioides and Melodorum leichhardtii.

3.32.6 Life history and ecology

There have been no studies made of the biology or autecology of Rhodamnia sp. (Calliope N.Gibson 1335) and because of its recent discovery there has been very little field observation and anecdotal evidence of its life history. Beardsell et al. (1993) have reviewed the reproductive biology of the Australian Myrtaceae while Lughadha & Proença (1996) have surveyed the reproductive biology of the Myrtoideae (Myrtaceae). There is no information presented in these reviews about the genus Rhodamnia.

A number of Rhodamnia species have been cultivated in Australia by the use of cuttings and seeds (Wrigley & Fagg 1996). Rhodamnia sp. (Calliope N.Gibson 1335) forms a tree up to 8 m high with a trunk up to 12 cm diameter and when mature is part of the upper stratum of the closed forest community. The longevity of individuals is unknown. It appears capable of resprouting from the base when the above-ground portion of an individual is killed (Plate 33). Most individuals observed were single trunked, except for two which were multistemmed from the ground level and appear to have developed from a resprouting event in the past.
Rhodamnia sp. (Calliope N.Gibson 1335) has been observed with immature fruits in December and mature fruits late January. Most mature plants observed in November were in the early stages of flowering with primordial flower buds present. Only one was in full flower. This individual appeared to be nearing its peak flowering and had numerous flowers clustered along the stems just below the end of the branchlets. There was a faint perfume emanating from the flowers and nectar was observed to be present. The Rhodamnia has unspecialised flowers that may attract a wide range of pollinators. The most common pollinators of Australian Myrtaceae are insects (Beardsell et al. 1993) and this is the most likely group to be the pollen vector for Rhodamnia sp. (Calliope N.Gibson 1335). An introduced honey bee (Apis mellifera) was observed visiting the flowers of Rhodamnia sp. (Calliope N.Gibson 1335) during fieldwork in November.
Rhodamnia sp. (Calliope N.Gibson 1335) has been observed in fruit in late January (J. Brushe pers. comm.). The fruits of Rhodamnia sp. (Calliope N.Gibson 1335) are 3-4 mm in diameter and 1 to 4 seeded. The seed is surrounded by a soft, fleshy tissue with a yellowish red skin on the outside suggesting dispersal may be effected by animals. Of possible animal dispersal agents, birds and bats are the most likely. Other Rhodamnia species in south east Queensland which have similar fruits have been observed to be ingested by birds (Church 1997). In Australian rainforests, the most important bird species for seed dispersal are probably pigeons (Adam 1992). Another possible dispersal mechanism is downslope movement of fruit by gravity.
In their review of the reproductive biology of Australian Myrtaceae, Beardsell et al. (1993) concluded that self-incompatibility was common in the family and appeared to be the main method of enhancing outcrossing. However, Lughadha & Proença (1996) commented that there are as many reports of self-compatibility in the Myrtoideae as those of self-incompatibility. If Rhodamnia sp. (Calliope N.Gibson 1335) is self compatible the loss of genetic variation through self -crossing may be a major threat to the long term viability of the species with its small population of scattered individuals.
Field observations suggest that there is presently a lack of recruitment of Rhodamnia sp. (Calliope N.Gibson 1335) at the site.
The very restricted distribution Rhodamnia sp. (Calliope N.Gibson 1335) may indicate that it is rather selective in its environmental requirements.
It is suspected that all stages of the life cycle of Rhodamnia sp. (Calliope N.Gibson 1335) are fire-sensitive.

3.32.7 Threats

There are two major threats to the remaining population of Rhodamnia sp. (Calliope N.Gibson 1335), fire and weed invasion of the habitat.

Large tracts of the vine forest to the north and northwest of the known plants have been previously destroyed by fires. This area is now densely covered with lantana (Lantana camara) (Plate 35). Two of the known plants of Rhodamnia sp. (Calliope N.Gibson 1335) are within 50 m of this area. Lantana is the most significant environmental weed at the site. Past timber harvesting opened up tracks along the ridges which have become overgrown with lantana. Lantana in the understorey at high density provides fuel loads which will support fires moving into the vine forest. There are also reports indicating that lantana can have an allelopathic effect on a range of plant lifeforms (Achhireddy and Singh 1984).
A continuing low population size may also be a potential threat to the species in the long term. A restricted gene pool and inbreeding could lead to loss of genetic variation which would threaten the long term viability of the population.

3.32.8 Management, Research and Conservation Measures

The continued decline of the species can only be averted by removing threats to the populations. A strategy needs to be drawn up to address the following issues.

The principal habitat management issue for this species is the protection of its vineforest habitat from fires. A total fire exclusion policy should be practised. Liaison is needed with Department of Primary Industries, Forestry and rural landholders adjoining the State Forest to alert the local community to the issue of fire management within the area.

The eradication of weeds, particularly lantana (L. camara) from the habitat. Lantana is present throughout the vineforest. Control of such large infestations of a weed species can only be successfully and economically achieved by biological agents. Research into the biological control of L. camara is currently being undertaken by staff of the Department of Natural Resources.

Further surveys of habitat are required to substantiate whether there are any more populations in existence. The habitat is difficult to traverse because of the steepness of the slopes and density of the vegetation. So far only a small portion of the potential habitat has been examined and further searching of the immediate locality is likely to add to the known population size of this species. Apart from other nearby vine forest sites, other possible habitats worthy of investigation include the western slopes of Kroombit Tops and the vineforest communities in the Kalpower area (W.J.F. McDonald pers. comm.).
There is little information available on the ecology and reproductive biology of Rhodamnia sp. (Calliope N.Gibson 1335). Studies into the factors affecting recruitment and establishment of individuals is required. Loss of genetic variation is potentially a major threat to the long term viability of small populations of rare plant species. Investigations should be initiated into the level and structure of genetic variation, and the breeding system of Rhodamnia sp. (Calliope N.Gibson 1335). These investigations should focus on determining strategies for conserving the genetic resources of this species.
The whole of the vine forest should be considered for protection. The declaration of a State Forest Scientific Area under the Forestry Act 1959 should be considered.
The present information indicates that Rhodamnia sp. (Calliope N.Gibson 1335) has a very small population which is geographically restricted, with an area of occurrence of approximately 60 hectares and an area of occupancy estimated to be 3500 m². The species is not conserved in any secure reserve. Rhodamnia sp. (Calliope N.Gibson 1335) assessed against the IUCN (1994) criteria for threatened wildlife falls into the category of Critical endangered, ie. is facing a high risk of extinction in the wild in the immediate future, as defined by criteria B.1, C.2 and D. B.1. Extent of occurrence estimated to be less than 100 km² or area of occupancy estimated to be less than 10 km², and known to exist at only a single location. C.2. Population estimated to number less than 250 mature individuals and a continuing decline inferred in numbers of mature individuals and population structure in the form of all individuals in a single subpopulation. D Population estimated to number less than 50 mature individuals. Rhodamnia sp. (Calliope N.Gibson 1335) has been proposed for inclusion on the schedule of threatened wildlife of the Queensland Nature Conservation Act 1992 as Endangered. This status is considered to be appropriate.

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