Hibbertia superans (a low spreading shrub) - endangered species listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the low spreading shrub, Hibbertia superans Toelken as an ENDANGERED SPECIES on Part 1 of Schedule 1 of the Act and, as a consequence, to omit reference to a population of Hibbertia incana (Lindley) Toelken in the Local Government Area of Baulkham Hills as an ENDANGERED POPULATION on Part 2 of Schedule 1 of the Act. Listing is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Hibbertia superans (Dilleniaceae), has been newly described by Toelken (2000), Notes on Hibbertia (Dilleniaceae) 3. H. sericea and associated species. J. Adelaide Bot. Gard. 19: 1-54. It is a 'low spreading shrub to 0.3 m high, with few to many, weak twisted stems and branches, villous when young, becoming tomentose with longer hairs more or less wearing off. Vestiture on all parts consisting of more or less long silky over a dense layer of usually short stiffly erect simple hairs, but particularly on the branches and the undersurface of leaves there are often some scattered stellate hairs with 2-3 (-5) equal erect branches (cf. variation below). Leaves (none modified into hypsophylloids) with axillary hair tuft below flowers 1-1.2 mm long; petiole 0-0.2 mm long; lamina linear, rarely linear-elliptic, (5.6- )7.5-10 (-12.3) x 0.9-1.2(-1.4) mm, acute, often becoming obtuse, scarcely constricted into petiole, slightly broadened central vein usually raised to same level as revolute margins and continued (0.4-0.6 mm wide in the middle) into the apex, with undersurface not visible, villous over or becoming tomentose above and below. Flowers single, sessile to slightly stalked, terminal on main branches or rarely on short shoot, younger ones freely overtopping older ones; bracts linear, 8.3-9.5 x 1.0-1.3 mm, like leaves with distinct central vein, villous sometimes becoming tomentose. Calyx not accrescent; outer calyx lobes linear-lanceolate, acute, with slender central vein and recurved margins in upper third, (6.8-) 7.5-9 (9.8) x 1.5-1.6 mm, much longer than inner ones, outside villous over or becoming tomentose, inside at least upper half like outside; inner calyx lobes oblong- elliptic to -obovate, obtuse to rounded, 4.2-6.5 (-7.6) x 1.9-2.7 mm, outside villous over more or less appressed pubescent, inside rarely with a few appressed hairs towards the apex. Petals broadly obovate, 5.5-6.7 mm long, emarginate. Stamens 6-9, subequal; filaments basally connate, but often some more than others; anthers narrowly oblong, (1.4-) 1.6-1.8 mm long, dehiscing mainly by lateral slits. Pistils 2; ovaries laterally compressed, each with 4 ovules; style from outer apex of ovary, curved outwards and around the cluster of stamens to end at the apex of the outer anthers. Fruit villous with very dense erect simple hairs. Seeds oblong-obovoid, often oblique, 1.5-1.7 x 1.1-1.4 mm, fleshy aril expanding into a scarcely lobed sheath adpressed to the base of seed, often to one side of base of seed. Flowering: July-Dec'.

2. Hibbertia superans is part of the H. sericea complex as published in the Flora of NSW. (Harden & Everett in Harden, G.J. (ed.) 1990, Flora of New South Wales Vol. 1, pp. 302-303, University of NSW Press, Kensington). It includes the population of H. incana occurring in Baulkham Hills Shire and listed as an endangered population in Part 2 of Schedule 1 of the Threatened Species Conservation Act.

3. Hibbertia superans grows in ridgetop woodlands. The species occurs from Castle Hill to South Maroota in the northern outskirts of Sydney, where there are some 14 currently known sites, and at one locality at Mt Boss, inland from Kempsey. The largest known population has been estimated to have about 400 plants. No populations are known from a formal conservation reserve.

4. Most occurrences are in or near Shale/Sandstone Transition Forest and are often associated with other threatened flora including Pimelea curviflora var. curviflora, Darwinia biflora, Epacris purpurascens var. purpurascens, Leucopogon fletcheri subsp. fletcheri, Acacia bynoeana, Eucalyptus sp. Cattai and Persoonia hirsuta. These plants tend to be very strongly associated due to their habitat requirements and restricted distribution.

5. Hibbertia superans is threatened by clearing for urban and rural residential development, disturbances to its habitat, weed invasion and road and rail maintenance.

6. In view of 3, 4 and 5 above the Scientific Committee is of the opinion that Hibbertia superans is likely to become extinct in nature in NSW unless the circumstances and factors threatening its survival or evolutionary development cease to operate.

Proposed Gazettal date: 05/10/01
Exhibition period: 05/10/01 - 0911/01