National recovery plan for Boronia granitica (Granite Boronia)

NSW National Parks and Wildlife Service, July 2002
ISBN 0 731 36889 4

1 Current conservation status

Boronia granitica Maiden & Betche (Granite Boronia) is known from less than ten disjunct areas of granitic outcrop vegetation on the north-western side of the New England Tablelands from near Armidale in New South Wales (NSW) to the Stanthorpe district in southern Queensland.

The species is currently listed as endangered (Schedule 1 Part 1) on the NSW Threatened Species Conservation Act 1995 (TSC Act). The 'endangered' code is reserved for species considered 'likely to become extinct in NSW unless circumstances and factors that threaten its survival or evolutionary development cease to operate', or 'numbers are reduced to such a critical level, or its habitats have been so drastically reduced that it is in immediate danger of extinction'.

A review process by the NSW Scientific Committee has resulted in a recommendation in May 2002 that B. granitica be downlisted to vulnerable on the basis that the total population size of the species is much larger than previously believed (NSW Scientific Committee 2002).

A summary of the conservation status of B. granitica is given in Table 1.

Table 1: Conservation status of Boronia granitica
Legislative or scientific list Code Status
NSW Threatened Species Conservation Act 1995
E
endangered
Commonwealth Environment Protection and Biodiversity Conservation Act 1999
E
endangered
ANZECC Threatened Australian Flora (ANZECC 1993)
E
endangered
Rare or Threatened Australia Plants (ROTAP) (Briggs and Leigh 1996)
3VC-
vulnerable
Vascular Plants of Conservation Significance in North-Eastern NSW (Richards et al. 1998)
C-1
critically threatened

Note:
E = endangered;
3 = a geographic range in Australia greater than 100 kilometres;
V = vulnerable, not presently endangered but at risk over a longer period (20-50 years) of disappearing from the wild through continued depletion, or occurs on land whose future use is likely to change and threaten its survival;
C- = at least one population within a proclaimed conservation reserve but population size not accurately known; and
C-1 = critically threatened.

2 Description

2.1 Taxonomic description

Boronia granitica is a medium-sized shrub with divided leaves and bright pink flowers. It was first described by Maiden and Betche in the Proceedings of the Linnean Society of New South Wales (1905) from Maiden and Boorman's 1905 type collection from Howell, south-east of Inverell in NSW. Detailed taxonomic descriptions are provided in Weston and Porteners (1991), Quinn et al. (1995) and Duretto (in press). Williams (1979) also provided an illustration of the species.

2.2 Taxonomic significance

The genus Boronia belongs to the Rutaceae, a plant family with a wide distribution throughout the warmer parts of the world. Rutaceae is predominantly a 'southern' family with a high degree of endemism (greater than 95 percent of species and greater than 50 percent of genera) in Australia (Morley and Toelken 1983). The tribe Boroniaea is the largest of the six Australian Rutaceae tribes, has the greatest number of endemic species and is particularly common and conspicuous among sclerophyll heathlands.

The genus Boronia is confined to Australia and New Caledonia with approximately 100 of the total 104 species endemic to Australia (Weston and Porteners 1991). Of this, approximately 35 species occur in NSW (Weston 1990).

B. granitica belongs to the section Valvatae, with the two closest congeners, B. repanda and B. boliviensis m.s. (formerly Boronia sp. J.), being the most threatened members of the section (Duretto in press) and possibly the rarest boronias in eastern Australia.

Although B. repanda is listed under the TSC Act, its natural occurrence in NSW requires confirmation. It may be present in Boonoo Boonoo National Park (NP) (G. Robinson pers. comm.) but the nearest confirmed records are confined to a small area of the granite belt in south-eastern Queensland (refer Appendix 3). If the existence of B. repanda cannot be confirmed in NSW then the species should be removed from the schedules of the TSC Act.

3 Distribution

3.1 Current and historical distribution

Boronia granitica occurs in the northern part of the New England Tableland and Nandewar biogeographic regions of NSW and southern Queensland as described in Thackway and Cresswell (1995). The species has been known for several decades from the type locality at Howell, north to the Stanthorpe district in southern Queensland. More recently the species has been collected approximately 50 kilometres south of Howell at Parlour Mountain near Armidale (Hunter and Bruhl 1997).

In NSW, B. granitica is currently known from several isolated populations (see Figure 1 and details in Table 2), one of which is critically small and possibly non-viable.

A 1933 specimen of B. granitica lodged in the NSW herbarium is labelled 'The Gorge', Kangaroo Creek near Elsmore, c. 16 kilometres east of Inverell. Information on the current status of B. granitica near Elsmore is lacking. Although small areas of suitable habitat may occur in the Elsmore district, it has not been botanically surveyed. Given no subsequent records (for more than 50 years) and the possibility of error in locality labelling of the original voucher, the presence of B. granitica near Elsmore seems dubious and requires confirmation.

The local government areas in which populations of B. granitica occur in NSW are Tenterfield, Inverell, Severn, Guyra and possibly Armidale Dumaresq Councils.

Location of known occurrences of Boronia granitica in New South Wales
Figure 1: Location of known occurrences of Boronia granitica in New South Wales
Table 2: Tenure of known population areas of Boronia granitica in New South Wales
Population area Land tenure Local Government Area No. of populations Estimated population size
Parlour Mountain (c. 35 km NW of Armidale) Private Freehold Guyra / Armidale Dumaresq
one
three plants
Howell (c. 20 km SW of Inverell) Leasehold & Permissive Occupancy Guyra / Inverell
multiple
Possibly hundreds
Kings Plains National Park Inverell
one
thousands
Severn River and 'The Barbs' near Pindari Dam Nature Reserve and Water Reserve Inverell
multiple
thousands
Torrington area State Recreation Area Tenterfield Severn
/ multiple
thousands

Note:
The Severn River and Kings Plains populations may not be totally isolated as there are scattered occurrences of B. granitica along the extent of the discontinuous band of granite and acid volcanic outcrops that broadly link the two areas (J. Hunter pers. comm.). Other populations can be considered isolated in a pragmatic management sense even though limited genetic exchange may still occur across intervening unsuitable habitat by vector transportation of pollen.

The Torrington area may represent a stronghold for B. granitica in NSW as several relatively large populations occur in suitable habitat over a range of approximately 40 kilometres from near Emmaville to Silent Grove. In a recent intensive survey of the vegetation of the Torrington SRA, Clarke et al. (1998) classified the distribution of B. granitica within the Torrington area as 'widespread' (as populations occur beyond a 10 kilometre radius), and 'frequent' (as the species was recorded in 14.5 percent of 246 sites surveyed). Additional herbarium records of B. granitica from the Torrington area are given in Table 3.

Table 3: Boronia granitica populations recorded from the Torrington area
Population location Estimated population size Year Collector / surveyor
The Gulf, near Emmaville
Not given
1905
Andrews
Bismuth
Not given
1970
J. Williams
Silent Grove
Not given
1971
G. Althofer
Butler Road
15
1990
White & Williams
Bismuth Falls
10-20
1990
White & Williams
Blatherarm Creek
c. 40
 
Williams et al.
Breakfast Creek track (off Gulf Rd)
Not given
1990
Quirico et al.
Flagstone Creek track (off Gulf Rd)
Not given
1990
Quirico et al.
Highland Home Creek Crown Lease
50
1996
Croft & Sheringham
Carpet Snake Gap
200
1997
L. Copeland
'Mystery Face'
c. 50
1998
J. Westaway

Note:
Some of the above populations may have also been surveyed by Clarke et al. (1998).

In the Stanthorpe area of southern Queensland approximately ten small populations of B. granitica occur on private, or otherwise unreserved, lands scattered over 30 kilometres extending from near The Summit, Thulimbah and Amiens villages south to Girraween NP (Queensland Herbarium records, Quinn et al. 1995).