National recovery plan for Boronia granitica (Granite Boronia)

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

Appendix 3: Boronia repanda in NSW

Introduction

Boronia repanda (Border Boronia) is a distinctive small shrub with simple foliage and pink flowers that grows in heathy woodland vegetation on granitic soils. The species is confined to a very limited area near Stanthorpe within the 'granite belt' of south-east Queensland. The occurrence of B. repanda in New South Wales (NSW) is equivocal and requires confirmation.

Legislative status

Boronia repanda is listed as endangered on both the NSW Threatened Species Conservation Act 1995 (TSC Act) and the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. The species is considered endangered and assigned a Rare or Threatened Australian Plant (ROTAP) code of 2E by Briggs and Leigh (1996).

Taxonomic description

Boronia repanda (F. Muell. ex Maiden & Betche) Maiden & Betche (Rutaceae) is a small shrub to 1 metre tall with simple oblong or elliptic leaves (to 18 millimetres long) that are thick, glandular and stellate hairy and have revolute glandular margins. Inflorescences are axillary, single-flowered and pedicellate, and the tomentose flowers have pale to bright pink (occasionally white) valvate petals that enlarge to 10 millimetres long and persist in fruit (Weston and Porteners 1991, Quinn et al. 1995). For a full taxonomic description see Duretto (in press). The species is illustrated in Williams (1979) and Weston and Porteners (1991).

Taxonomic significance

From a 1904 collection from Stanthorpe, Maiden and Betche first described Boronia repanda as B. ledifolia var. repanda noting that the specimen was most closely related to B. ledifolia. B. repanda remains within the B. ledifolia group (Weston et al. 1984) and is the sister species of B. granitica (Duretto in press). B. repanda differs from other members of Boronia section Valvatae of the 'granite belt' by having simple leaves.

Habitat

Boronia repanda grows in heath and woodland on sandy granitic soils often in association with granite boulders (Weston and Porteners 1991, Quinn et al. 1995, Duretto in press). Quinn et al. (1995) lists the following as associated species: Allocasuarina sp., Boronia anemonifolia, Cryptandra sp., Daviesia sp., Eriostemon myoporoides subsp. epilosus, Eucalyptus andrewsii and Exocarpos sp.

At Jolly's Falls, north of Stanthorpe, B. repanda occurs at low frequency in low open forest dominated by Eucalyptus andrewsii and E. banksii on a steep southern slope with few scattered granite boulders. A sparse secondary tree layer of Callitris endlicheri and Leptospermum trinervium occurs above a moderately dense shrub stratum dominated by Acacia betchei, Hovea purpurea, Notelaea linearis, Mirbelia confertiflora and Dodonaea hirsuta.

B. repanda has been collected flowering between July and November and with fruit in October and November. Very little is known of its life history, ecology or response to disturbance, though it is apparently fire-sensitive (Quinn et al. 1995).

Distribution

Boronia repanda is confined to a small portion of the 'granite belt' and appears to have an extremely narrow distributional range of less than 20 kilometres. Quinn et al. (1995) list nine population localities in the Stanthorpe district of Queensland, all of which are pre-1975 collections.

Approximately 20 specimens lodged in herbaria (Duretto in press) are presumably collections from the same nine localities, with more recent collections from Cottonvale (Duretto 1992 voucher in Melbourne herbarium) and Jolly's Falls (Westaway 1998 voucher in Coffs Harbour regional herbarium).

B. repanda is listed as occurring in NSW (Weston and Porteners 1991, Briggs and Leigh 1996). The only collections from NSW are those made by Hickey from the Maryland area, approximately 10 kilometres north-east of Stanthorpe on the Queensland/NSW border. There is a possibility that these historic 19th century specimens may actually have been collected in Queensland as Maryland Station apparently extended at that time across the border into Queensland (W. McDonald pers. comm.). B. repanda has not subsequently been recorded from the Maryland area and a recent search along roadsides in the Maryland-Stanthorpe area failed to reveal suitable habitat on the New South Wales side of the border (Quinn et al. 1995).

Other records of B. repanda in NSW such as those provided from the National Parks and Wildlife Service Wildlife Atlas cannot be substantiated and therefore are regarded as invalid. The species presence in NSW therefore remains equivocal.

Threats and current conservation status

Boronia repanda has not been collected from a national park and no populations are known to occur in any conservation reserve (Quinn et al. 1995, Duretto in press). Clearing has occurred around the known locations and most populations appear to be in small patches of remnant vegetation or in heavily disturbed areas. Populations have almost certainly been eliminated by clearing for pine plantations, which occur up to hill tops and ridges (Quinn et al. 1995).

Agricultural expansion and clearing of remnant vegetation continue to be threatening processes (Duretto in press). A high fire frequency would also pose a serious threat to B. repanda populations as the species is apparently fire-sensitive and its dry sclerophyll forest and heath habitat is prone to frequent fires (Quinn et al. 1995).

B. repanda is probably the most threatened member of Boronia section Valvatae (Duretto in press) and possibly the most threatened Boronia in eastern Australia. However, its occurrence in NSW requires confirmation (Quinn et al. 1995, Richards et al. 1998) and further surveys are needed to ascertain the exact distribution and status of the species in both NSW and Queensland (Duretto in press).

Recommendations

  • contract a botanist, familiar with Boronia repanda and the granite flora of the New England Tablelands, to collate all existing information pertaining to the species, its distribution and habitat;
  • utilise computer predictive models to derive the distribution of mapped environmental attributes common among known sites to predict further occurrences. This will only be possible if sufficient environmental data exist and are accessible from Queensland authorities;
  • utilise aerial photograph interpretation to examine remnant vegetation stands on granite in proximity to the NSW border for the same vegetation 'phototype' as that of known Queensland localities which may indicate the occurrence of similar habitat in NSW;
  • locate potential habitat on topographic and cadastral maps;
  • liaise with relevant landholders to acquire property access; and
  • undertake detailed targeted field searches for B. repanda.

Should the existence of the species in NSW be confirmed, specimens supported by accurate and detailed locality data should be collected and lodged with the appropriate herbaria. Upon validation of any such records of the species in NSW, the current listing as endangered under the TSC Act and the ROTAP conservation code of 2E would be maintained. Obligations under the TSC Act would then require the preparation of a recovery plan for B. repanda as a priority.

Alternatively, should a reasonable level of habitat survey and targeted species search effort fail to locate B. repanda in NSW, the species should be recommended for downlisting or deletion from the schedules of the TSC Act.

References

Briggs, J.D. and Leigh, J.H. (1996). Rare or Threatened Australian Plants. CSIRO Publishing, Collingwood.

Duretto, M.F. (in press). Systematics of Boronia section Valvatae (Rutaceae). Muelleria.

Quinn, F.C., Williams, J.B., Gross, C.L. and Bruhl, J.J. (1995). Report on rare and threatened plants of north-eastern New South Wales. Report prepared for NSW National Parks and Wildlife Service and Australian Nature Conservation Agency.

Richards, P.G., DeVries, R.J. and Flint, C. (1998). Vascular plants of conservation significance in north-eastern New South Wales: inventory and assessment. Unpublished draft report, NSW National Parks and Wildlife Service, CRA Unit, Northern Zone.

Weston, P.H., Caroline, R.C. and Armstrong, J.A. (1984). A cladistic analysis of Boronia Sm. and Boronella Baill. (Rutaceae). Australian Journal of Botany 32: 187-203.

Weston, P.H. and Porteners, M.F. (1991). Boronia. In: Flora of New South Wales (Ed) G.J. Harden Vol 2, pp. 227-236. New South Wales University Press, Kensington.

Williams, K.A.W. (1979). Native Plants of Queensland. 1:33.