Pultenaea glabra Benth., Fl. Austral.

Renner, Matthew A. M., Barrett, Russell L., Clarke, Steve, Clugston, James A. R. & Wilson, Peter H. Weston Trevor C., 2022, Morphological and molecular evidence refute a broad circumscription for Pultenaea glabra (Fabaceae: Mirbelieae), with implications for taxonomy, biogeography, and conservation, Australian Systematic Botany 35 (3), pp. 225-277 : 239-242

1. Pultenaea glabra Benth., Fl. Austral. 2: 125 (1864)

Type citation: ‘ N. S. Wales. Blue Mountains , R. Cunningham.’ Type: New South Wales, Blue Mountains , s. dat., R.Cunningham s.n. (lecto: K, fide R.P.J.de Kok and J.G.West, Austral. Syst. Bot. 15: 94 (2002); isolecto: MEL 2055289 !, K) .

Erect, usually single-stemmed, woody shrub up to 2.2 m tall, openly branched in upper third into a spreading crown; branching pattern furcate or whorled; branchlets pale yellow–green, glabrous. Stipules red–brown or red–purple at base, black–brown towards the tips, aging to black–brown throughout, furcate, lobes triangular, straight, not arched or recurved, sometimes acuminate, keeled and coriaceous medially, membranous marginally; red–brown, lamina and lobe margins denticulate; divided up to ~0.6 times length when associated with sterile leaves. Leaves linear to linear-oblanceolate, but only faintly oblanceolate, 9.4–20.9 (average 14.5) mm long, 0.8–2.1 (average 1.4) mm wide, flat, margins plane; adaxial surface with glaucous bloom owing to sparse, low pill-box shaped papillae, glabrous; apex apiculate, red–brown. Leaf anatomy with subepidermis of faintly pigmented orange–brown cells one tier deep immediately above the ventral epidermis either side of the median vascular trace and extending two-thirds of the way to the leaf edge; three vascular traces present, the medial largest, lacking enlarged cells below the medial trace. Inflorescence terminal on shoot that ceases growth; leafy throughout although leaf length decreases from the base to the apex of the inflorescence; internodes contracted; stipules associated with flowers broader than those associated with leaves, with shorter lobes and longer disc. Flowers shortly pedicellate, pedicels glabrous, but with long red–brown trichomes present in axils. Calyx heavily suffused with red on margins, otherwise pale green; outer surface glabrous, inner surface with a floccose covering of short, dense hairs towards and on lobe margins; lobes apiculate; margins hyaline, bordered wine-red, medially green. Bracteoles narrow triangular, acuminate, with broad membranous light brown or fawn ‘wings’ either side of a coriaceous medial band, extending beyond adjacent calyx sinus; glabrous or with a few short marginal hairs. Corolla midyellow, other pigments largely absent; standard with very faint red markings at base; keel paler than standard, pale yellow with a green wash that intensifies towards the applegreen base; standard broadly ovate with cordate base, folded along the medial line and so embracing the wings and keel, margins weakly inrolled; wings narrow obovate above a narrow stipe, basal auricle narrow, its apex broadly rounded but asymmetric; keel asymmetrically obovate–elliptic above a narrow stipe, with straight upper margin and evenly rounded apex, its basal auricle triangular, with a narrowly rounded apex. Ovary and style glabrous. Pods ~ 5 mm long ( Fig. 9 , 10 ).

Distribution and ecology

The known distribution of Pultenaea glabra extends from the Kings Tableland in the south to the vicinity of Mount Tomah in the north. The most easterly known population occurs at Hazelwood Dam at Lawson, and the most westerly population on the south side of the Grose River is at Katoomba, with historical records further west from Mount Victoria, whose source populations may or may not be extant. Collections of Pultenaea glabra from the upper Grose River catchment between Blackheath and Mount Tomah are in the vicinity, but to the east, of Mount Victoria and may represent more recent gatherings from the same ‘Mount Victoria’ population. The only population currently known on the northern side of the Grose River occurs ~ 3 km west of Mount Tomah on the southern side of the Bells Line of Road. Outside of this area, all records of Pultenaea glabra are based on other species, including P. euchila , P. mutabilis , P. aculeata , and P. weindorferi , among others. A previous report from Parramatta is based on the type of P. villosa var. glabrescens , which is in fact a synonym of P. flexilis , and a previous report from Blackheath is based on P. euchila . Records of P. glabra from Lithgow, Hartley and Sydney, could not be confirmed during our study and are likely to be based on misidentifications, or on cultivated material. We have not seen specimens on which the historical record from Dubbo is based, but suspect this too is a misidentification. Reports from Victoria are all referable to P. weindorferi , those from Queensland to other, unrelated species. Pultenaea glabra in the stricter sense resolved here is endemic to a smaller range than previously appreciated, and couples this narrower geographic distribution with fairly precise microsite preferences. Pultenaea glabra is associated with sites in close proximity to free-flowing water, or on sites with reliable subsurface soil moisture. Riparian vegetation alongside streams including on streambanks and alluvial terraces, and short or tall vegetation in gully heads including on the margins of hanging swamps may all contain P. glabra as a component of the shrub layer. All known sites occur over Narrabeen group sandstone bedrock, in soils that are either peaty (as at Bullaburra) or with a high clay content (as at Empire Pass, Lawson), depending on the microsite. Pultenaea glabra may occur as scattered individuals within a mixed shrub layer beneath Eucalyptus - dominated forest with more or less continuous canopy, as at Mount Tomah, or as a dominant component of streamside riparian vegetation, with many contiguous plants in dense shrubbery beneath a discontinuous forest canopy, as at Hazelwood Dam, and Frederica Falls.

Recognition

Pultenaea glabra possesses a combination of characters encompassing many aspects of form, from the branching architecture through to leaf micromorphology and anatomy, that facilitate ready identification of plants, in both herbarium and field. The branching architecture of P. glabra is distinctive, being furcate or whorled, because shoots are terminated by inflorescences, and vegetative growth is continued by branches that issue from below the inflorescences. The form of the inflorescence is also characteristic, because within the inflorescence, internodes separating sequential flowers are much shorter than those separating adjacent leaves in vegetative shoot sectors. Further, within the inflorescence, the leaves and their pedicels subtending each flower are progressively reduced in size from the base to the apex of the inflorescence, to the point where they are not expressed. The stipules subtending and within the inflorescence are large and imbricate. The calyx is glabrous, and the bracteoles are coriaceous and also glabrous. The branchlets are glabrous, as are the oblanceolate leaves, which are discolourous, being glaucous above due to the presence of low columnar papillae. Characters that discriminate P. glabra from other species of the P. glabra complex, and other relatives, are presented in Table 2 .

Pultenaea glabra may hybridise with P. flexilis to produce hybrid individuals that grow to maturity alongside individuals of P. glabra . The hybrids are more similar to P. glabra than to P. flexilis in leaf morphology, because they have narrow oblanceolate leaves bearing a glaucous bloom on the adaxial surface, rather than the oblong leaves lacking a glaucous bloom as in P. flexilis . However, the leaves of hybrid individuals are consistently wider than the leaves of pure P. glabra individuals, with a measured range of 1.5–2.8 mm and an average width of 1.9 mm, compared with a range of 0.8–2.1 mm and an average width of 1.4 mm in P. glabra . Hybrids are readily distinguished from pure P. glabra when they are in flower, because their flowers are not contracted in a terminal inflorescence, and although they may group towards the end of shoots, they are separated by internodes of more or less normal length, and are subtended by normal leaves ( Fig. 11 ) as in P. flexilis ( Fig. 12 ).

Pultenaea glabra has been confused with P. mutabilis , but is readily distinguished by the patterns of flower production, the leaf shape, as detailed in Table 2 , but perhaps most readily by the branchlets, which are hairy with appressed antrorse hairs in P. mutabilis , and glabrous in P. glabra .

Variation

There is some variation among individuals in flower size; individuals in the population on the northern side of the Grose River may have larger flowers than those on the southern side, but individuals with large and small flowers are both present in this population.

Notes

Pultenaea villosa var. glabrescens Benth. was listed as a synonym of P. glabra by de Kok and West (2002). However, the type specimen ( K 000118985) is a better match with P. flexilis , the synonymy of which we transfer this name, below.

Conservation status

The geographic distribution of P. glabra is smaller than previously understood, and its microsite preferences are narrower than previously recognised. Most of the known populations of P. glabra occur within or immediately adjacent to the suburban corridor flanking the Great Western Highway, on council or private land. Some populations are under threat from invasive weeds including Ligustrum sinense Lour. and Lonicera japonica Thunb. ex Murray , possibly facilitated by elevated nutrient levels in runoff from upstream peri-urban areas. Populations on the northern side of the Grose River were burnt during the 2019–2020 fire season, with the likely result that the all adult plants were killed, although this has not been confirmed. Like other members of the P. glabra complex, P. glabra probably experiences extreme fluctuations in the numbers of adult individuals as a result of fire, and recovering populations are vulnerable to depletion by short fire-return times. As circumscribed here, Pultenaea glabra may qualify for listing as Endangered under the IUCN criteria ( IUCN 2012), given the extent of occurrence is less than 5000 km 2, the quality of habitats is likely to continue to decline as weed invasions progress, and severe fire years result in extreme fluctuations in the number of mature individuals.

Specimens examined

NEW SOUTH WALES: Central Tablelands: Mt Tomah, ~ 100 m downslope from Bells Line of Road and ~ 3.5 km east of Mt Tomah , 10 Oct. 2013, C. D. Kilgour 3011 ( NSW 908496 ); Mount Victoria, Oct. 1910, W. F. Blakely s.n., ( NSW 38077 ); Wentworth Falls , Sep. 1893, R. T. Baker s.n., ( NSW 467168 ); Wentworth Falls , 20 Oct. 1959, D. F. Blaxell s.n., ( NSW 100242 ); Wentworth Falls , Jan. 1898, R. T. Baker s.n., ( NSW 467169 ); Wentworth Falls (Bodington Road), Hanging Swamp , Blue Mountains , near Bodington Hospital , 23 June 1999, J. Anderson s.n., ( NSW 431580 ); Within grounds of Bodington Aged Care, Tableland Road , Wentworth Falls , 1 Feb. 2006, S. Rose s.n., ( NSW 738435 ); 5 km S of Wentworth Falls , 300 m along the road N of the entrance of the car park of Queen Victoria hospital. On left side of road if travelling north, 5 Dec. 2000, R. P. J. de Kok 910, L. Orthia, C. Servase , ( NSW 506489 ); Kings Tableland, Wentworth Falls, 6 1/ 2 miles [~ 10.4 km] by road from the Western Highway , Apr. 1962, C. E. B. H. Burgess s.n., ( NSW 61038); Wentworth Falls , 24 Dec. 1950, H. St. John 24897, ( NSW 38082 ); Andersons Firetrail turnoff, Kings Tablelands Rd , near Wentworth Falls , 2 Oct. 1985, A. Auld 36, ( NSW 218436 ); Leura , Jan. 1908, J. T. Wilson s.n., ( NSW 38071 ); Katoomba Falls , 29 Nov. 1932, W. F. Blakely s.n., ( NSW 38080 ); 7.6 km SE of Queen Victoria Hospital, Wentworth Falls on the McMahons Lookout Rd , close to Anderson Fire Trail , 17 Sep. 1985, R. G. Coveny 12151, W . Bishop, R. O . Makinson, ( NSW 218666 ); Leura, ex Herbarium F. A . Rodway no. 1742, Apr. 1916 H. M. R. Rupp s.n., ( NSW 38074 ); Leura , Jan. 1915, A. A. Hamilton s.n., ( NSW 38078 ); Leura Cascades , 1 Nov. 1985, A. Auld 32, ( NSW 218441 ); Leura Falls , Dec. 1907, A. A. Hamilton s.n., ( NSW 38073 ); Leura Falls , Nov. 1913, A. A. Hamilton s.n., ( NSW 467166 ); Hazelbrook , Sep. 1914, A. A. Hamilton s.n., ( NSW 38075 ); Adelina Falls, Lawson , 7 Oct. 1986, R. G. Coveny 12363, K. U . Kramer, M . D. Tindale, ( NSW 507730 ); Lawson, track to Frederica Falls , 26 Oct. 1982, R. G. Coveny 11311, P .D. Hind, T. James, ( NSW 467167); Bullaburra, below Boronia Road and Boronia Reserve on south side of Great Western Highway, 6 Oct. 2018, M. A. M. Renner 9044 & L. J. Gray, ( NSW 1052694); ibid, 6 Oct. 2018, M. A. M. Renner 9045 & L. J. Gray, ( NSW 1052712); 6 Oct. 2018, M. A. M. Renner 9046 & L. J. Gray, ( NSW 1052713); 6 Oct. 2018, M. A. M. Renner 9047 & L. J. Gray, ( NSW 1052714); 6 Oct. 2018, M. A. M. Renner 9048 & L. J. Gray, ( NSW 1052715); 6 Oct. 2018, M. A. M. Renner 9049 & L. J. Gray, NSW 1052716; Central Coast: Hazelbrook, road to dam, Woodford Creek, 26 Sep. 2018, M. A. M. Renner 9037 & R. L. Barrett, ( NSW 1052815); 26 Sep. 2018, M. A. M. Renner 9038 & R. L. Barrett, ( NSW 1052816); 26 Sep. 2018, M. A. M. Renner 9040 & R. L. Barrett, ( NSW 1052818); 26 Sep. 2018, M. A. M. Renner 9041 & R. L. Barrett, ( NSW 1052819); 3.5 km W of Mt Tomah, 1 Oct. 2019, M. A. M. Renner 9160 & L. J. Gray, ( NSW 1058858); 1 Oct. 2019, M. A. M. Renner 9161 & L. J. Gray, ( NSW 1058861).

Figures

Fig. 9. Pultenaea glabra line drawing. (a) Habit, (b) flowering branch detail, (c) flower, side view, (d) standard petal, (e) keel, (f) wing, (g) magnified calyx, side view, (h) ovary detail, (i) stem detail showing stipule, (j) leaf, adaxial surface, (k) leaf, abaxial surface, (l) leaf surface detail, abaxial, (m) leaf surface detail, adaxial. Scale bar: 26.7 mm (a), 10 mm (b), 8 mm (c–f), 4 mm (g), 2.7 mm (h), 5.3 mm (i), 5 mm (j, k), 1.6 mm (l, m). All from NSW 1058858, a from dried material, b–m from spirit.

Fig. 10. Pultenaea glabra photos. (a, b) Flowers showing arrangement in a terminal head subtended by reflexed leaves, and absence of normal leaves among flowers. Also evident are the glabrous calyces. (c) Flowers showing the concave standard, red nectar guides, and green wash on the keel. (d) Flowers from below, showing the consistent expression of a green wash to the keel. (e–g) Three views of flowering shoots showing the inflorescence comprising closely spaced flowers terminating the shoot, and the whorl of reflexed leaves subtending the inflorescence. All from plants growing at Bullaburra, in the vicinity of voucher NSW 1052715.

Fig. 11. Pultenaea flexilis × P. glabra photos. (a) Flowering shoot showing the production of flowers close to the shoot apex, with normal leaves subtending each flower, which are separated by internodes that are not contracted. (b) Portion of a vegetative shoot showing the oblanceolate leaves that have a hint of the angular base as occurs in P. flexilis, but which bear the distinct glaucous bloom of P. glabra. (c–e) Close up of an inflorescence showing the flowers produced close to the shoot apex, the glabrous calyx with coriaceous bracteoles, the flowers subtended by normal leaves, and note the conspicuous mid-vein on the underside of the leaf, where the leaf underside is visible. All from the Lawson population of P. glabra at Hazelwood dam, in the vicinity of voucher NSW 1052820.

Fig. 12. Pultenaea flexilis photos. (a) Flowering shoot showing production of flowers in the axils of normal leaves; note the conspicuous mid-vein on the abaxial leaf surface. (b) A flowering shoot bearing a cluster of flowers at its apex, with each flower subtended by a normal leaf, and the shoot continuing vegetative growth from amidst the flowers. (c) A flowering shoot from below, showing the production of buds in the axils of leaves on short lateral branches, and the conspicuous mid-vein on the leaf abaxial surface. (d) Close-up of flowering shoot showing the glabrous calyx with short triangular inconspicuous bracteole, and the short linear stipules that are similar in size on vegetative leaves and below flowers. (e) A flowering shoot from above, showing a loose cluster of flowers at the shoot apex, each subtended by a normal leaf, although this does progressively reduce in size. (f) The same shoot as in e in lateral view, illustrating how similar a terminal group of flowers in P. flexilis can appear to those in P. glabra, despite their different fundamental structure.