National recovery plan for the Endangered Native Jute Species, Corchorus cunninghamii F. Muell. in Queensland (2001-2006)

Marion Saunders
Rainforest Ecotone Recovery Team (RERT)
Environment Australia, 2001

2. Background

The genus Corchorus belongs to the family Tilaceae and includes approximately 100 individual species of herbs and sub-shrubs which are distributed world-wide, primarily in tropical and sub-tropical regions. Twenty-six species belonging to the genus Corchorus are found in Australia, twenty one of which are considered to be endemic.

C. cunninghamii F. Muell. is an endemic, perennial, flowering herbaceous shrub with small yellow flowers and soft leaves with serrated margins. The species was first described in 1862 from material collected from south-east Queensland by Baron Ferdinand von Mueller. More recently the species was thought to be extinct as it had not been collected in the wild for almost forty years (1944 to 1983). However, since 1983 populations of C. cunninghamii have been located in a limited area around south-east Queensland and north-eastern New South Wales.

In 1995 a conservation statement and draft recovery plan for C. cunninghamii was prepared by David Halford (1995a). This original plan provided the basis for the current plan and as such is acknowledged here.

2.1 Species description

C. cunninghamii is a herbaceous, perennial shrub which grows to a height of 1.5 metres in the wild but may grow to 2 metres when cultivated. The stems are often though not always reddish in colour, and either smooth or sparsely covered with minute hairs. Leaves are 5-15cm long, 1.5-5cm wide, attached to stalks (petioles) 1-2.5cm long. They are characteristically smooth, narrowly ovate to ovate or elliptic ovate, with a finely serrated margin and a tip that tapers to an obvious point. Leaves are three-veined from near their base and arranged in an alternate pattern around the stem. Stipules, the growths at the base of a leaf stalk or stem that resemble leaves, measure up to 1mm in length, are ovate, red, fleshy, hairless, and have a single nectar secreting pore under their surface.

The flowers are small, have four yellow, narrow, oval-shaped petals measuring 9-11mm long and 3-5mm wide. They may grow as a cluster of 2-7 flowers originating from a single stalk located at the side of an upper stem opposite a leaf, or singularly at leaf or flower nodes. Buds are pear-shaped with a diameter of 3-4mm. Four pale yellow to green pointed sepals 7-11mm long are evident at the base of the flower or bud. Flowers contain 60-80 stamens and a weakly, three or 4-ribbed ellipsoid ovary (1.5-3 mm long and 4-6 mm wide), consisting of three or four cells each with 18 to 21 ovules. Although the species has been recorded to flower throughout the year, the peak flowering period for C. cunninghamii is from November to May (Halford, 1995a; b).

Fruiting bodies form on the plant between December and May but they may also be found at other times of year. They are characteristically narrow, dark brown to black, ellipsoid-shaped capsules measuring 1.5-3.5cm long and 4-6mm wide. The capsules contain three or four chambers each with 2-22, elliptical or rounded, matt brown to black seeds 2-3mm in length. Unlike the fruiting bodies of other Australian members of the Corchorus taxa which split from the apex downward, the capsules of C. cunninghamii split longitudinally with the apex of the fruit remaining intact. C. cunninghamii is closely related to others in its genus (C. hygrophilus, C. reynoldsiae and C. thozetti) but can be distinguished by its narrowly elipsoid capsule. The species is relatively easy to identify when flowering but at other times may be confused with other superficially similar species, including Abutilon oxycarpum (flannel weed) and Trema tomentosa (poison peach).

Other descriptions of the species may be found in Stanley and Ross (1986), Harden (1990) and Halford (1995a; 1995b).

 Corchorus cunninghamii. Diagram provided by the Queensland Herbarium
Figure 1: Corchorus cunninghamii. Diagram provided by the Queensland Herbarium

2.2 Distribution

Although some of the early records held by the Queensland Herbarium for C. cunninghamii have imprecise locations, it appears that the species was previously found in an area ranging from Brisbane in Queensland to Lismore in New South Wales (Halford, 1995a). Early Queensland specimens were recorded from the Moreton Bay region, Ithaca Creek, Peechey's Scrub and Enoggera areas. In 1932 and 1944 C. cunninghamii was recorded at Mount Cotton in Queensland and near Kyogle in New South Wales, respectively. These were the last collections of the species recorded until 1983 when it was found in Pullenvale, a western suburb of Brisbane. In 1988 another population was located south of Brisbane in the Darlington Range and in 1992 a single plant was recorded at Brookfield, a western suburb of Brisbane. More recently field work conducted by Halford, as part of a conservation statement and draft recovery plan (1995a), indicated that there were only four locations with extant C. cunninghamii populations. These were at Brookfield, Ormeau (Darlington Range) and Wongawallan in Queensland, and at Toonumbar in NSW Further information regarding existing populations of the species in NSW can be found in the NSW recovery plan for C. cunninghamii (NSW National Parks and Wildlife Service, 1999) and in Stewart (2000).

 Distribution of Corchorus cunninghamii populations in Australia (from Parr, 2001).
Figure 2: Distribution of Corchorus cunninghamii populations in Australia (from Parr, 2001).

Since 1995, populations of C. cunninghamii have also been identified at both Brisbane Forest Park (BFP) and Mount Cotton. Site information for the ten existing Queensland populations, the number of plants at each site (Table 2 and 3) and their size class distribution (Figure 3) are provided below. The Brookfield site has been omitted from the current recovery plan as only one plant existed at this site in 1993 and given the short lifespan and reproductive requirements of the species it is unlikely to exist today. In addition this plant existed on privately owned land, in a highly modified habitat and there was some doubt as to whether it was a natural occurrence of the species or whether it was accidentally introduced with other plants obtained from Pullenvale nursery, where the species was known to occur naturally and was cultivated (Halford, 1995a).

Table 2: Population numbers for Corchorus cunninghamii at Queensland sites. Population estimates obtained from: 1Halford (1995a); 2Simmonds (2000); 3Parr (2001)
Site
1993 1
1998 2
2000 2
2001 3
1
262
not counted
44
562
2
69
not counted
14
63
3
5452
not counted
239
> 5000
4
28
not counted
14
8
5
8
not counted
4
4
6
unknown population
>100
604
50
7
unknown population
unknown population
17
153
8
unknown population
100
91
9
9
unknown population
unknown population
1
1
10
unknown population
8
4
28
TOTAL
5, 819
 
1, 032
> 5, 878
 Size class structure of the Queensland populations (from Parr, 2001).
Figure 3: Size class structure of the Queensland populations (from Parr, 2001).

Wongawallan

Three populations, all within a 1km radius occur at the Wongawallan location, which is 16km south-east of Beenleigh and 8km north-east of Eagle Heights. The sites are contained within the Gold Coast City Council Shire and the Pimpama Creek catchment area. The Wongawallan location is 6km south of the Ormeau sites (Sites 4 and 5) and accessible from the Tamborine-Oxenford Road. Elevation at these sites is between 320 to 355m. Soil is derived from metamorphic rocks known as the Neranleigh-Fernvale Beds and is shallow, brown to black in colour and has a loam to medium clay texture.

The vegetation structure of the area is open forest with Eucalyptus crebra (narrow-leaved ironbark), Eucalyptus propinqua (grey gum), Eucalyptus microcorys (tallow wood) and Eucalyptus acmenoides (white mahogany) the predominant trees in the overstorey. The lower stratum is variable between sites and diverse in nature, although Senna barclayana (pepper leaf senna), Lantana camara (lantana), Trema tomentosa (poison peach), Solanum stelligerum (devil's needles), Acalypha nemorum (hairy acalypha) and Abutilon oxycarpum (flannel weed) are conspicuous understorey elements.

The number of plants at all three sites showed a substantial decline between the years 1993 and 2000. However, population counts conducted in 2001 showed that the population size had increased to levels similar to, or greater than those in 1993. This increase is likely to have been facilitated by a fire which passed through the area in November 2000. Apart from this fire and some recreational use of the area the Wongawallan sites have remained relatively undisturbed over recent years. Visits to the sites in 2001 showed that a dirt track which runs alongside Sites 1, 2 and 3 is also used by motorcyclists. However the level of use is currently low and C. cunninghamii seedlings continue to grow on the paths edge. Other rare or threatened plant species that are present at the Wongawallan sites include Endiandra floydii, Sophora fraseri (brush sophora), Macadamia integrifolia (macadamia nut) and Randia moorei (spiny gardenia).

Site 1: Wongawallan 1

Site 1 is located on the crest of ridge which runs in a north westerly/south-easterly direction and covers a 225m2 area. Of the three Wongawallan sites, this site is drier and more open than the others. It also has a grassy understorey which contains Hibiscus heterophyllus (native hibiscus) and the weed species Lantana camara (lantana). Both of these species are likely to compete with C. cunninghamii. The number of plants at Site 1 increased from 44 in 2000 to over 562 in 2001. It would appear that the fire that passed through the area at the end of 2000 has stimulated germination of the seed bank at this site, given that a noticeably younger cohort was present in 2001 than in 2000. The population at Site 1 is currently on freehold land with the owners being aware of the presence of an endangered plant species on their property. It may be possible to secure protection of this site in the future though a voluntary conservation agreement (VCA) with the owners, via a parkland dedication if parts of the site are ever put forward for further development, or through the Gold Coast City Council purchasing this piece of land for conservation purposes, as it has done for Site 3.

Site 2: Wongawallan 2

This site is located on a hillcrest with a north easterly aspect, 1-2° slope and covers an area of approximately 225m2. Compared to the other sites at this location it is more mesic and has a dense coverage of ferns such as Hypolepis glandulifera (downy ground fern), Lastreopsis marginans (glossy shield fern), Doodia aspera (prickly rasp fern), Calochlaena dubia (false bracken) and Pteris tremula (tender brake fern). The number of individuals at Site 2 has increased from 14 individuals in 2000 to 63 in 2001, although this number is still less than that recorded in 1993. The population also appears to have expanded in area since 2000 as some individuals were found almost 5m away from the edge of this site, which was marked by tape previously. The small size class and single height cohort suggests seedling recruitment since 2000 has resulted from the fire that passed through the area recently. In addition, a large fallen log which currently divides the population is likely to have caused disturbance to the soil seed bank, as well as extending the area that C. cunninghamii covers at this site. Land tenure is Road Reserve, although the road is not constructed. The Gold Coast City Council is responsible for the management of the site.

Site 3: Wongawallan (Wilkies Scrub Conservation Area)

Site 3 is located on a hillcrest and hillslope with a south-easterly aspect, a 5° slope and covers 800m2 of open forest. C. cunninghamii is the predominant plant species in the understorey at this site. In 1993 the size of the population was estimated at 5452 individuals, which was over 90% of the total number of plants in both Queensland and New South Wales at the time. It appeared from the similar age class of the individuals that some event, such as the fire which went through the area some time in 1991 or 1992 stimulated an increase in population numbers at this site. By 2000 the number of plants recorded at Site 3 had declined to only 239 individuals. Since this time another fire has passed through the area and the population has increased once again to over 5000 individuals. Of all the existing populations in Queensland this site continues to support the largest number of plants and is one of the most easily conserved and managed in the long-term. In 1995, when the original conservation statement and draft recovery plan for the species was written (Halford, 1995a), the land tenure of Site 3 was held in Freehold by a local farmer. On the 16th of June 2000, the property was acquired by the Gold Coast City Council under the Council's Open Space Preservation Levy and it is now considered Council Reserve. Other plant species of importance at Site 3 include the threatened ecotonal plant species Endiandra floydii and Sophora fraseri (brush sophora). Additional rare or threatened plant species occurring at the Wilkies Scrub Conservation Area include Baloghia marmorata (jointed baloghia), Cryptocarya foetida (stinking cryptocarya), Cupaniopsis newmanii (long-leaved tuckeroo), Pararistolochia pravenosa and Randia moorei (spiny gardenia).

Ormeau (Darlington Range Nature Refuge)

Two populations of C. cunninghamii occur at the Ormeau location, which is situated about 6km north of the Wongawallan sites and 10km south-east of Beenleigh. The sites occur within a radius of approximately 500m, cover a total area of 525m2, and can be accessed via Cliff Barron's Road. The sites are contained within the Gold Coast City Council Shire and the Pimpama Creek catchment area. In 1995, when the conservation statement and draft recovery plan for C. cunninghamii was written, this land was owned by Readymix Quarry (CSR). Discussions between CSR, the Ormeau progress association and former Albert Shire Council have led to the area being set aside for the preservation of C. cunninghamii and the adjacent vine forest. The management of the Ormeau location is now undertaken by the Environmental Protection Agency and the land on which C. cunninghamii grows is owned by the Public Trustee and considered part of the 'Edward Corbould Reserve and Nature Refuge' (Gazettal date; 18/10/96).

Although the C. cunninghamii populations at Ormeau occur in open forest with a sparse to mid-dense lower stratum they are closely associated with the open forest-subtropical rainforest ecotone. Elevation at the sites is between 160 to 180m and common overstorey trees include Eucalyptus propinqua (grey gum), Lophostemon confertus (brush box) and Eucalyptus crebra (narrow-leaved ironbark). A predominant shrub in the lower stratum at the Ormeau sites is the weed species Lantana camara (lantana). This weed species forms dense thickets in the rainforest and open eucalypt forest ecotone and is one of the threatening processes for C. cunninghamii at this location. The lower stratum is diverse and includes shrubs, ferns sedges and grasses such as Polyscias elegans (celery wood), Astrotricha latifolia (silver leaf), Acalypha nemorum (hairy acalypha), Psychotria daphnoides (smooth psychotria), Acacia aulacocarpa (brown sandalwood), Adiantum hispidulum (rough maidenhair-fern), Oplismenus aemulus (creeping shade grass), Doodia aspera (prickly rasp fern and Carex declinata. Several other rare or threatened floral species occur in the area adjacent to the C. cunninghamii populations at Ormeau. These include Choricarpia subargentea (giant ironwood), Macadamia integrifolia (macadamia nut), Pouteria eerwah (black plum) and Randia moorei (spiny gardenia).

Soil at the Ormeau site is derived from the metamorphic rocks known as the Neranleigh-Fernvale Beds which consists of greywacke, argillite, quartzite, chert, shale, sandstone and greenstone. It is shallow and stony, dark brown to black-brown in colour and medium clay in texture. The fire and disturbance history of the Ormeau sites is largely unknown and there is no evidence to suggest that the populations have been disturbed in recent times (May and July, 2001). In 1995, David Halford concluded that from the thickness of the leaf litter that fire had been absent for a very long time and from a personal communication with Glenn Leiper, Melanie Simmonds (2000) stated that the area had not been burnt for at least ten years. The continued presence of plants, though low in number, indicates that germination of seeds at this location has occurred independently of soil heating by fire. It is possible, as suggested by David Halford (1995) that germination of seedlings at this location is triggered by animal foraging.

Site 4: Ormeau 1

This site is located on an upper hillslope with a south-easterly aspect, a 20° slope and covers an area of approximately 300m2. The number of C. cunninghamii plants at this site has declined from 28 individuals in 1993, to 14 in 2000. In July 2001 there was a further decline to only eight individuals. Without some form of intervention this population is likely to disappear given that it is a small isolated population, there is a thick vegetative cover of the introduced weed species Lantana camara (lantana), and there has been no fire or other obvious disturbance to the area for many years. The recovery of this population is dependent on the viability of the soil seed bank, which may have been severely diminished over time.

Site 5: Ormeau 2

Given the close proximity, there are obvious similarities between Site 4 and Site 5 with regard to their physical description and threats to the populations long-term viability. Both sites are located in open forest, have medium clay soils and are located on an upper hillslope with a 20° incline. In addition, Site 5 covers an area of approximately 225m2 and has an easterly aspect. The population number at Site 5 has declined from eight individuals in 1993, to only four plants in 2000. Examination of the site in July 2001 revealed that there were still only four plants at this site. However, all of these individuals were seedlings and as such were not the same plants observed in the 2000 census. As no other living plants were found at this site in 2001 it is possible that not all specimens were located, or that they had died and not been found. Nevertheless it is clear that this population, like that at Site 4 is in decline and is likely to disappear without some form of site management.

Brisbane Forest Park

Four populations of C. cunninghamii occur at Brisbane Forest Park (BFP), which covers an area of approximately 28, 500 hectares and is located in the foothills of the D'Aguilar Range, approximately 34km from the city of Brisbane. These populations were not identified until the late 1990's. The sites at which C. cunninghamii populations occur in BFP cover a total area of approximately 9, 400m2 and are located less than 20km from each other. Elevation at the sites ranges between 100 and 170m. Soils from the three sites (Sites 6, 7 and 9) located around Enoggera Reservoir, are of a clay loam type and are derived from Bunya-Phyllite rock. At Site 8, which is the most westerly of the populations, soil has a loam consistency and is derived from the Neranleigh-Fernvale Group.

Since elevation, temperature and rainfall within the park vary greatly, vegetation is diverse. Populations of C. cunninghamii at sites 6 and 7 occur in an open forest/subtropical rainforest ecotone and populations at Sites 8 and 9 occur in an open forest/wet sclerophyll forest ecotone (Simmonds, 2000). A common canopy species at all sites is Lophostemon confertus (brush box) and other canopy species include Eucalyptus siderophloia (grey ironbark), Eucalyptus propinqua (grey gum), Eucalyptus microcorys (tallow wood) and Corymbia citriodora (spotted gum) (Parr, 2001). The introduced weed species Lantana camara (lantana) and Rivina humilis (coral berry) are present in the understorey.

Site 6: BFP 1 - Fursman's Scrub/Peninsula Site

This site is located north of Enoggera Reservoir and is contained in the Enoggera Creek catchment area, and of all the sites is located closest to BFP headquarters. The population is situated on a hillcrest with a south-easterly aspect, a 10° slope, and covers an area of 8,000m2. It occurs on land held in 'water supply reserve', and is under Brisbane City Council control. Common canopy species at Site 6 include Lophostemon confertus (brush box) and Corymbia citriodora (spotted gum). The site was discovered by BFP staff in 1998, after a high intensity fire passed through the area in March of that year. A few months after this fire the C. cunninghamii population was estimated to be in excess of 100 plants and by November 1999 the number of plants had increased to 604. It should be noted that a high intensity fire probably occurred at this site in 1970. In 1999/2000 Site 6 contained the largest population of C. cunninghamii in Queensland (Simmonds, 2000). However since this time the population has shown a substantial decline to only 50 individuals (Parr, 2001). It is likely that this decline has resulted from a lack of disturbance in recent times. This is supported by the observation that the majority of individuals at this site are less than 30cm tall (Figure 1) and occur alongside a vehicle trail that separates the population. Slashers and bulldozers have been used infrequently to maintain this trail for four wheel drive access.

Site 7: BFP 2 - McDonald's Scrub Site

The McDonalds Scrub site is located on the west side of Enoggera Reservoir, is contained in the Enoggera Creek catchment area and covers and area of about 400m2. This site, like Site 6, is held in 'water supply reserve' and is managed by the Brisbane City Council. The C. cunninghamii population is located on a densely vegetated lower hillslope, with a 5° incline and faces a north-easterly direction. The species was originally identified at this site in 1997 by Kenneth MacClymont who works for the Brisbane City Council and is an active member of the Brisbane Rainforest Action Information Network (BRAIN). Site 7 differs from others at BFP in that it has undergone an active weed reduction program over recent years, and is the only population to have increased in number since 1999/2000. Weeds, particularly Lantana camara (lantana), have been removed by hand as part of a rainforest restoration project implemented by BRAIN at this site in 1996. Since 1996 weeding has occurred on another two occasions, the most recent of which was in June 2001. It is likely that this weeding program has contributed to the increase in C. cunninghamii numbers from 17 in 2000, to 152 in 2001. Other disturbances that are likely to have facilitated this population increase are a low intensity fire that passed through the area in August 2000, and the soil trampling that occurs as a result of individuals hiking through the area for recreation or other purposes. It should be noted that a high intensity fire has probably not occurred at this site since 1970.

Site 8: BFP 3 - Lake Manchester Site

Site 8 is located approximately 20km, in a south-westerly direction, from Sites 6, 7 and 9. It is located in land held by Brisbane City Council in 'Fee Simple' and covers an area of 1,000m2. The site occurs in the Lake Manchester catchment area. The C. cunninghamii population at site 8 occurs on a hillcrest, with a south-easterly aspect and a 5° slope. This site is drier and than the other BFP sites and is the most densely populated by Lantana camara (lantana). C. cunninghamii was originally discovered near Lake Manchester by bushwalkers in mid 1998, a year or two after Brisbane City Council re-opened an existing but neglected fire break with slashers and four wheel drive tractors. Population numbers were estimated at 100 in 1998 and 91 in 1999/2000. Since this time the population has shown a substantial decline to only nine individuals. This decline is largely due to the site being over-run by lantana and a lack of disturbance. The most recent fire that occurred in the area was conducted by BFP and Forestry staff in April, 1997. This late summer burn was of low intensity and was thought to have missed the C. cunninghamii population. Although the population at Lake Manchester is in decline, recovery is possible if the site contains a viable seed bank.

Site 9: BFP 4 - Mount Aurum Scrub Site

The Mount Aurum Scrub site occurs on the north-west side of the Enoggera Reservoir, is contained in the Enoggera Creek catchment area and is located in 'Forest Reserve'. Characteristic canopy species include Eucalyptus propinqua (grey gum), Eucalyptus microcorys (tallow wood) and Lophostemon confertus (brush box). C. cunninghamii was originally discovered at Mount Aurum Scrub in November 1999 by BFP staff looking for gold mines in the area. At this time a single plant was located on a south-easterly facing hillslope with a 10° aspect. In 2001 this individual was once again located (Parr, 2001), however no additional plants were found at this time. Vegetation surrounding the plant has not been obviously disturbed in recent times, and although there have been plans to burn this site in the last two years weather conditions have not been suitable. The last recorded fire at this site was of low intensity and occurred in 1986. Of all C. cunninghamii populations in Queensland this one is most likely to disappear.

Mount Cotton

Site 10: Mt Cotton

C. cunninghamii plants were at identified at Mount Cotton in 1996, by a member of the Society for Growing Australian Plants (SGAP) while on a field trip. Although the species had previously been recorded at this location no plants had been collected from the wild, from this or any other location in Queensland from 1944 to 1983.

The Mount Cotton site is located about 26km south-east of the city of Brisbane and occurs in Redlands Shire Council and the Tingalpa Creek catchment area. It can be accessed from Mount View Road and is located on a hillcrest, with a south-easterly aspect, 230m elevation and 10° slope. Downhill from this site, on an adjacent property, is the privately owned 'Rainforest Gardens', which has introduced large numbers of exotic plants to the area. The C. cunninghamii population occurs in open forest, on sandy loam soil derived from Neranleigh-Fernvale rock and covers an area of approximately 120m2. Vegetation at the site is diverse and includes trees like Eucalyptus propinqua (grey gum), Eucalyptus acmenoides (white mahogany), Corymbia intermedia (pink bloodwood), Acacia bakeri (marblewood), Acacia perangusta, Lophostemon confertus (brush box), Ficus fraseri (sandpaper fig) and Macadamia integrifolia (macadamia nut). It also contains a large range of native shrubs, herbs, grasses, sedges, ferns, orchids and vines, in addition to a number of exotic species like Lantana camara (lantana), Bidens pilosa (cobblers pegs) and Rivina humilis (coral berry).

The number of C. cunninghamii plants at Mount Cotton has increased from four individuals in 2000, to 28 in July 2001. Most of these plants are seedlings less than 30cm tall (Figure 1) and are clustered in a 6m2 area, on the edge of a path that provides access to a Telstra tower near the site. A region surrounding the path was cleared by brushcutters some time early in 2001 and it appears that this disturbance may have facilitated the germination of seeds. Other types of disturbance that have occurred in recent times are a fire that passed through the area in 1995 and the regular grazing of cattle. Although the recent census has shown that the number of plants has increased at this site the population is far from secure. Since the discovery of this population Rivina humilis (coral berry) has increased its dominance in the shrub layer and exotic plants, introduced to the area by the owners of 'Rainforest Gardens', are growing up towards the C. cunninghamii population. These exotic plants and their associated garden clippings, as well as the dispersal of seeds from these non-native plants by animals or birds in the area, may eventually threaten the uniqueness of this site if not managed effectively. Similarly, inappropriate disturbances or ill-timed disturbances may be a problem if the site is not secured and grazing and brush cutting continue to occur in an ad hoc manner.

Of the 28 plants that exist at the Mount Cotton site, 22 plants occur on land that is held in 'Road Reserve' tenure and is managed by the Redlands Shire Council. The remaining six individuals are located on privately owned land. The owner has shown little interest having an endangered plant species on his property and has indicated that he may eventually build close to the site. Redlands Shire Council is now considering purchasing the portion of land on which these plants reside. A major reason for conserving the Mount Cotton population is that individuals at this site are genetically different to those at other Queensland locations (Simmonds, 2000), and as such may be valuable in enhancing the genetic variation of the species in the long-term.

Table 3: Site summary for Corchorus cunninghamii populations in Queensland (for further information see Section 2.2 and 2.4).
Site
Location
Latitude/ Longitude
Land Tenure/Site Protection
Number of Plants (2001)
Threats
1
Wongawallan
Gold Coast City Council- Pimpama Creek Catchment 27° 51'000S
153° 14'018E
Freehold
562
Exotic weed invasionInappropriate fire regimePossibly grazing and recreation
2
Wongawallan
Gold Coast City Council- Pimpama Creek Catchment 27° 51'11S
153° 14'00E
Road Reserve
63
Exotic weed invasionInappropriate fire regimePossibly grazing and recreation
3
Wongawallan
Gold Coast City Council- Pimpama Creek Catchment 27° 51'13S
153° 12'52E
Wilkies Scrub Conservation Area- purchased by the Gold Coast City Council (2000)
> 5000
Exotic weed invasionInappropriate fire regimePossibly grazing and recreation
4
Ormeau
Gold Coast City Council- Pimpama Creek Catchment 27° 48'13S
153° 12'30E
Part of the Edward Corbold Reserve and Nature Refuge (1996)
8
Low population number (inbreeding depression)Exotic weed invasionInappropriate fire regimePossibly grazing
5
Ormeau
Gold Coast City Council- Pimpama Creek Catchment 27° 48'30S
153° 12'33E
Part of the Edward Corbold Reserve and Nature Refuge (1996)
4
Low population number (inbreeding depression)Exotic weed invasionInappropriate fire regime Possibly grazing
6
Brisbane Forest Park
Brisbane City Council- Enoggera Creek Catchment 27° 26'44S
152° 55'17E
Water Supply Reserve under Brisbane City Council control
50
Exotic weed invasionInappropriate fire regime Possibly grazing, recreation and damage from slashing alongside trails
7
Brisbane Forest Park
Brisbane City Council- Enoggera Creek Catchment 27° 27'01S
152° 54'12E
Water Supply Reserve under Brisbane City Council control
153
Exotic weed invasionInappropriate fire regime Possibly grazing and recreation
8
Brisbane Forest Park
Brisbane City Council- Lake Manchester Catchment 27° 28'26S
153° 47'33E
Fee Simple land held by Brisbane City Council
9
Low population number (inbreeding depression)Exotic weed invasionInappropriate fire regime Possibly grazing, recreation and damage from slashing alongside trails
9
Brisbane Forest Park
Brisbane City Council- Enoggera Creek Catchment 27° 26'37S
152° 53'55E
Forest Reserve
1
Low population number (inbreeding depression)Exotic weed invasionInappropriate fire regime Possibly grazing and recreation
10
Mount Cotton
Redlands Shire Council- Tingalpa Creek Catchment 27° 36'907S
153° 12'847E
Road Reserve and freehold land
28
Exotic weed and non-native plant invasionInappropriate fire regime Possibly clearing, grazing, recreation and damage from slashing alongside trails
TOTAL
     
> 5, 878
 
Population estimates and latitude/longitude values obtained from Parr, 2001. All populations occur within the southeast Queensland bioregion.

2.3 Critical habitat and populations

In general populations of C. cunninghamii occur on upper hillslopes or hillcrests with a south-easterly or easterly aspect (Halford, 1995a; Simmonds, 2000). This aspect is moister, cooler and has less exposure to solar radiation than other aspects. The species is closely associated with the subtropical rainforest-open eucalypt forest ecotone and common canopy species that occur alongside C. cunninghamii include Eucalyptus propinqua (grey gum), Lophostemon confertus (brush box) and Eucalyptus siderophloia (grey ironbark). The vegetative composition and density of the understorey is variable between sites. However, at most sites introduced weed species such as Lantana camara (lantana), Rivina humilis (coral berry) and Ageratina adenophora (crofton weed) are present. The location of C. cunninghamii populations show no association with a particular elevation or geology, although soils are shallow, stony and well drained with a loam or clay consistency.

All existing populations of C. cunninghamii occur in the southeast Queensland bioregion (IBRA) with the Wongawallan sites occurring on land characterised by regional ecosystem (RE) 12.11.2 and the remainder of the populations by RE 12.11.5 (Sattler and Williams, 1999). Given that the conservation status of neither of these ecosystems is 'of concern at present' and both are represented in protected areas, and the ten C. cunninghamii populations occur at sites with no particular physical characteristics in common, there would not appear to be critical habitat for the species. However, at least seven of the ten populations appear to be critical to the survival of the species (see individual site descriptions in Section 2.2 for specific information). Currently four (Sites 4, 5, 8 and 9) of the ten existing populations have less than ten individuals and are likely to disappear without effective management and one population (Site 6) has declined 12-fold since the 2000 census. Other critical populations for the species include one at Mount Cotton (Site 10) which is genetically distinct from those at other locations and as such may be necessary to preserve the genetic diversity of the species in the long-term and one site at Wongawallan (Site 3) which currently has more than 85% of the total number of plants in Queensland. Although this site would appear to be thriving presently, in recent years numbers have not been constant at this site. Population estimates declined from 5452 in 1992 to only 239 in 2000 and have now increased to over 5000 individuals. This fluctuation reflects how susceptible the species is to extinction at a particular site if not effectively monitored and managed.

2.4 Life History and Ecology

Lifespan and reproduction

C. cunninghamii is a perennial, herbaceous plant with a short lifespan of approximately three to four years (Halford, 1995a). The growth rate for newly emerged seedlings has been estimated at 11mm per day, while the average growth rate of young mature individuals (50-75cm in height) was 33cm per year (Simmonds, 2000). For mature plants the growth rate was higher during October to April than for the cooler months of the year (April-October). A previous field study by Halford (1995a) indicated that of individuals that had germinated between March to May, 29% flowered and 12.5% had produced fruit in December of that year. Thus the species would appear to be capable of reproduction within a year of germinating. C. cunninghamii is not capable of vegetative reproduction and its propagation is dependent on the production of seed. Breeding studies/pollination trials indicate that the species is self-incompatible (Halford, 1995a; Simmonds, 2000), which is a problem for populations that are small and isolated. Effective reproduction of the species would appear to be reliant on pollinator activity of insects such as the introduced honey bee (Apis mellifera), native honey bees or stingless bees (Trigona sp.), sand wasps (Bembix sp.) and possibly ants (Halford, 1995; Simmonds, 2000).

Flowering and fruiting

In south-east Queensland C. cunninghamii produces its characteristic small yellow flowers primarily between the months of October and May, although some individuals appear to flower throughout the year (Halford, 1995a; Cameron, 1997). Plants in cultivation tend to flower for about two months at a time, and individual flowers remain open for only one day (Halford, 1995a).

Green, narrow, ellipsoid shaped fruiting capsules appear on the plant primarily between the months of December and May. As the capsule matures it darkens to a dark brown/black colour and splits longitudinally to release its seeds.

Seed dispersal and germination

Seeds of C. cunninghamii drop to the ground and are not forcibly ejected from the fruiting capsule and as such dispersal distances are generally short. Some seed dispersal is also likely to arise through the activity of foraging birds or animals and through the transport of seed in soil trapped in tyres of slashers, track graders or recreational vehicles (Stewart, 2000). It is also possible that seeds are transferred from one site to another on the soles of shoes.

C. cunninghamii seeds are released in a dormant state and appear to require some factor such as heat or other mechanical disturbance to facilitate their germination (Halford, 1995a; Cameron, 1997; Simmonds, 2000). Studies conducted by Halford (1995a) showed that most C. cunninghamii seeds are viable (82 and 98%) but that the proportion of dormant seeds was as high as 98%. Manually nicking the seed coat with a knife was effective in breaking the dormancy of 84% of seeds and oven temperatures of 80, 90, 100 and 107° C gave germination rates of 14, 47, 38 and 28% respectively. A similar effect was observed when boiling water was applied to seeds. In the absence of the boiling water pre-treatment only 1.3% of seeds germinated but when boiling water was applied 55% of seeds germinated (Cameron, 1997). Smoke in the presence of high temperatures has also been shown to facilitate seed germination (Simmonds, 2000). Given the low level of seedling recruitment that occurs under natural conditions the species is likely to accumulate a persistent soil seed bank. Germination studies have indicated that collected seeds remain viable for at least three years (Simmonds, 2000) but the longevity of soil stored seed is unknown.

Role of fire and disturbance

Seed germination trials and field observations have indicated that disturbance in the form of heat/fire or mechanical disturbance is necessary to promote the germination of C. cunninghamii seeds. Disturbance benefits however, are dependent on the type, intensity and frequency of the disturbance. Monitoring studies conducted by Halford (1995a) revealed that a 80% of seedlings at the Ormeau in Queensland (Sites 4 and 5) occurred in areas where the ground had been disturbed by animals. This sort of natural disturbance, which is likely to occur continually, would over time produce a population with a mixed age structure. Other types of mechanical disturbance or activities that appear to have facilitated the germination of C. cunninghamii seeds at particular sites include brushcutters and tractors (Sites 6, 10), recreation (Sites 3, 7), weeding (Site 7), grazing (Site 10) and forestry (NSW sites: Stewart, 2000).

A positive germination response to fire has also been observed at a number of Queensland populations, particularly Sites 1, 2, 3 and 6. Most noticeable is the change in population numbers observed at the Wongawallan 3 site (Table 2). A high-intensity fire passed through this area in sometime in 1991/1992 and again in November 2000. Population counts conducted one to two years after these fires indicated that more than 5,000 individuals occurred at this site. However the 2000 census, which was conducted prior to the 2000 fire, showed that the population had declined to 239 individuals over a period of eight years. These observations suggest that the fluctuation in population numbers recorded at this site was related to the fire history of the area.

As an obligate seed regenerator, persistence of the species after fire is dependent on the presence and germination of soil stored seed. If fires are too frequent plants may have insufficient time to build up the soil seed bank to replace plants that are killed in the fire. By contrast, a low intensity fire may be unable to stimulate the germination of seeds, particularly if they are buried deeply (Simmonds, 2000). The timing of the fire may be important as seasonal differences (e.g. rainfall, soil temperatures, amount of sunlight) are also likely to effect seedling recruitment (Stewart, 2000). Although the germination of C. cunninghamii seeds are facilitated by fire, further research is needed to determine what the optimal frequency, intensity and timing of these fires should be to sustain or enhance population numbers.

Threatening processes

Populations of C. cunninghamii are declining in both Queensland and New South Wales. Threatening processes such as clearing, habitat loss, weed invasion, inappropriate fire regimes, grazing, recreation and timber harvesting would all appear to be contributing to this decline. Clearing and habitat modification is likely to have been responsible for extinction of the species at Pullenvale and other locations in Queensland and NSW For example, over the years the Pullenvale area has been subdivided into residential blocks and the vegetation has been cleared or substantially modified through the introduction of non-native plants by landowners. At all locations exotic weed species such as Lantana camara (lantana), Ageratina adenophora (crofton weed) and Rivina humilis (coral berry) pose a threat to C. cunninghamii through competition and habitat alteration. Given that relatively high temperatures are beneficial for the germination of C. cunninghamii seeds, tall dense thickets of lantana may also reduce fire intensity and frequency and this may in turn have a detrimental impact on the long-term survival of the species. Although many of the above-mentioned factors are generally considered threatening processes, it should be noted that some disturbance is beneficial to the species and as such the impact of these threatening processes needs to be assessed on a site-by-site basis.

Genetics and morphology

Preliminary cytological studies indicate that C. cunninghamii is a natural tetraploid, with a chromosome number of 2n=28 (Halford, 1995a).

Isozyme studies have been used to determine the level of genetic diversity within and between populations of C. cunninghamii in Queensland and NSW (Simmonds, 2000). Individuals from all 13 known populations (10 in Queensland; 3 in NSW) were found to be homozygous at the 15 loci examined indicating that genetic diversity in this species is low. The mean expected panmictic heterozygosity (He) value for C. cunninghamii was 0.087, which is lower than that reported for other short-lived perennial herbaceous species (He= 0.116) but similar to that of other endemic species (He= 0.096). Of concern is the fact that the mean number of migrants (Nm) was determined to be 0.00. In general values greater than one are considered necessary to prevent local differentiation between populations due to genetic drift (Slatkin, 1987). Mean genetic distance between populations was 0.102 (range 0.0000-0.2624), which is high compared to some other Australian trees and woody shrubs (Sampson et al., 1995). Unique alleles and loci identified in the Mount Cotton and Toonumbar (NSW) populations increased the genetic distance between the populations and revealed that the Mount Cotton site is genetically located between the other Brisbane populations and Toonumbar. These studies indicate that populations in Queensland and NSW will need to be conserved in order to maximise the genetic diversity of the species.

Morphological variations in leaf, fruit, flower and stem characteristics have been noted between populations of C. cunninghamii (Halford, 1995a). However, studies conducted by Simmonds (2000) indicated that leaf characteristics (width and length) were not significantly different between populations, and suggested that minor differences may be due to site microclimatic conditions. Morphological differences between populations requires further investigation.

Propagation and cultivation

Over the years C. cunninghamii has been cultivated by the Brisbane Botanic Gardens, North Coast Botanic Gardens in Coffs Harbour and the Australian National Gardens in Canberra (Halford, 1995a). In the 1990's, a population was established at the Brisbane Botanic Gardens from seeds previously collected from the Pullenvale area in Queensland. The species had been recorded at Pullenvale in 1983 but had not been seen at this site for many years before seeds, which had been stored by the North Coast Botanic Gardens, were provided to the Brisbane Botanic Gardens for germination and the eventual re-introduction of the species to the Pullenvale location. The effectiveness and status of this re-introduction program is currently unknown and needs to be investigated. C. cunninghamii plants established at Brisbane Botanic Gardens have also provided valuable information regarding the reproduction and growing condition requirements of the species (Cameron, 1997; Simmonds, 2000). Plants appear to prefer a sheltered site with sufficient sunlight and well-drained, cool soil since prolonged periods of soil moisture can lead to bacterial rot of stems and roots (Halford, 1995a; Cameron, 1997). In addition plants may be grown from soft or hard tip cuttings, with the latter being a more successful method (Halford, 1995a). It should be noted that most of the cultivated material is likely to have originated from only a few individuals and populations, and as such should not be relied on to rescue the species from extinction.

2.5 Reasons for listing

C. cunninghamii is a naturally rare species due to its restricted geographical distribution, low level of seedling recruitment in the absence of fire or other mechanical disturbance, and the fact that the species has a short lifespan and is not self-compatible, requiring other individuals in close proximity in order to produce seed. Although the number of individuals currently in the wild is relatively high (approximately 6000 individuals) and the number of populations has increased since 1993 in Queensland, as recently as 2000 the total number of individuals was estimated at only 1032 individuals. This fluctuation reflects how susceptible this species is to extinction if populations are not effectively monitored and managed in the long-term. At some sites, population numbers are currently so low that they are likely to disappear unless some form of natural disturbance, or human intervention is able to facilitate the germination of seeds (if present) from the soil seed bank in the near future.

A further concern is that genetic diversity within populations of C. cunninghamii are very low. This may reduce individual fitness in the short-term and lower the populations viability and ability to adapt to change in the long-term.

The species is also threatened by weed invasion. Dense infestations of Lantana camara (lantana) and other introduced weed species threaten to displace surviving populations and alter the subtropical rainforest-open eucalypt forest ecotone that C. cunninghamii grows in.

2.6 Existing conservation measures

C. cunninghamii is listed as an endangered species in Queensland and New South Wales under the under the Queensland Nature Conservation (Wildlife) Regulation, 1994 (Schedule 2, Part 2) and the New South Wales Threatened Species Conservation Act, 1995 (Schedule 1) respectively. It is also listed as Endangered by the Commonwealth under the Environmental Protection and Biodiversity Conservation Act, 1999. As an endangered plant species it is an offence to, or to attempt to gather, pluck, cut, pull up, destroy, dig up, fell, remove or injure a protected plant or any part of a protected plant, other than under those exceptions listed under Sections 62 (1) and 89 (1).

Most of the known populations of C. cunninghamii occur in protected areas, or land that is secured by conservation agreements, ownership or tenure. In Queensland, the largest Wongawallan and both Ormeau sites have been secured since the original conservation statement and draft recovery plan was written in 1995 (Halford, 1995a). However, until sustainable land management strategies are implemented, with respect to fire and disturbance regimes, the species is far from secure.

New South Wales is also currently preparing a recovery plan for C. cunninghamii and conducting research into the life history, population dynamics and the role of fire and mechanical disturbance in the long-term management of the species. A shared interest in conserving in-situ populations of C. cunninghamii and the exchange of information between states (Queensland and NSW) is likely to benefit the conservation of the species in the long-term.