Hakea oligoneura K.A.Sheph. & R.M.Barker, Nuytsia 19(2): 253–258 (2009).
Hakea sp. Yalgorup (B.J. Keighery & N. Gibson 897), Western Australian Herbarium, in FloraBase, http://florabase.dec.wa.gov.au [accessed 2 Nov. 2009].
Shrubs 1.8–2 m high and up to 2 m wide. Bark smooth or finely fissured. Branchlets terete with dense, appressed, ferruginous or white, simple hairs 0.2–0.4 mm long, glabrescent. Leaves alternate, narrowly elliptic to oblanceolate, flat or rarely shallowly concave, 21–68 mm long, 4.5–10 mm wide, narrowly attenuate towards the base, spinose-dentate, with (0-)1–5 mucros per margin, margin straight or shallowly curved between each mucro, rarely entire, apex acute, mucro 0.1–0.5 mm long, glabrous or with infrequent, adpressed hairs 0.1–0.4 mm long; longitudinal veins 1–3(4), prominent above and below, secondary venation obscure.
Inflorescence axillary, almost sessile; rachis 1–2 mm long, with dense, stiff, white hairs 0.3–0.5 mm long. Bracts ovate, strongly concave, 0.5–2.4 mm long, 0.6–1.6 mm wide, with adpressed white hairs 0.1–0.2 mm long, caducous. Flowers 6–14. Pedicel 1.2–2.4 mm long, glabrous. Perianth 2.5–3.5 mm long, glabrous, white; limb recurved in bud, broadly elliptic, 0.7–1.1 mm long, 0.4–1.1 mm wide; tepals 4 splitting to base after anthesis; anthers 0.4–0.5 mm long, 0.2–0.3 mm wide. Torus oblique; gland vestigial, globular, 0.2–0.3 mm long or absent. Pistil 2.8–3.6 mm long; pollen presenter conical, 0.4–0.6 mm long; pollen yellow; ovary stipe 0.3–0.6 mm long.
Fruit almost sessile, down-curved, broadly ovoid, 1.1–1.8 cm long, 5.5–11.5 mm wide, beaked, pustulate and ridged, splitting almost to the base. Seed along upper side of follicle, obliquely ovate, 8–12 mm long, 4–5 mm wide, black; seed body 2.6–4.4 mm long, 2–2.8 mm wide; wing extending fully or almost fully down both sides of the seed, wider on the upper edge.
Reproduced from Nuytsia 19(2): 253–258 (2009).
Distribution and ecology
Currently only known from a few isolated populations in
H. oligoneura is found growing in white-brown sand on limestone ridges in open Mallee (Eucalyptus decipiens and E. patrensis) over Melaleuca acerosa, Xanthorrhoea and Hibbertia.
To plot an up to date distribution map based on herbarium collections for this species see Australia's Virtual Herbarium. Localities outside the native range may represent cultivated or naturalised records.
Flowers August to September.
Derivation of name
From the Greek oligo (few) and neuron (nerve), a reference to the lack of obvious secondary venation of the leaves, a feature that distinguishes this species from its closest relatives, H. anadenia and H. undulata .
Part of the Conogynoides group recognised by Bentham and characterised by a conical pollen presenter, veined leaves, glabrous perianth and fruits without horns.
Within this section 12 species were assigned to the informal Undulata group by Barker et al. (1999). This group of Hakea species was combined morphologically because they all have simple flat leaves with 3-7 prominent longitudinal veins, 10-40 small flowers (with 3-10.5 mm long pistils) and decurved woody fruits.
Members of the group are H. ambigua, H. anadenia, H. dactyloides, H. elliptica, H. falcata, H. ferruginea, H. hastata, H. laevipes, H. loranthifolia , H. neurophylla, H. plurinervia and H. undulata , from the eastern states and from SW WA. The newly described H. oligoneura (Nuytsia 19: 254 (2009) from the SW coast of WA belongs with this group.
H. oligoneura is most closely allied with H. anadenia and H. undulata, but is readily distinguished from both by the lack of any secondary venation between the main longitudinal veins and its leaves with only 1–5 mucros per margin; the other two species have prominent reticulated secondary venation and 5-10 mucros per side. The leaves of H. undulata are in addition always considerably wider than those of H. oligoneura (20-65 mm vs 4.5-10 mm wide).
Thanks to Kelly Shepherd (WA Herbarium) for providing photos of this species.
In Western Australia denoted as Priority Four - Rare: taxa (as Hakea sp. Yalgorup (B.J. Keighery & N. Gibson 897)), which are considered to have been adequately surveyed and which, whilst being rare (in Australia), are not currently threatened by any identifiable factors. These taxa require monitoring every 5–10 years.
Atkins, K.J. (2008). Declared Rare and Priority Flora List for
W.A. (all Yalgorup NP): 20 Sep. 2003, P. Foreman 379 (PERTH); 20 June 2002, P. Foreman & J. Kelly TT 125 (PERTH); 19 Sep. 1993, B.J. Keighery & N. Gibson 896 (PERTH); 19 Sep. 1993, B.J. Keighery & N. Gibson 897 (PERTH); 19 Sep. 1993, B.J. Keighery & N. Gibson 907 (PERTH); 25 Aug. 1993, G.J. Keighery 14992 (PERTH); 6 Mar. 1994, G.S. McCutcheon GSM 2869 (PERTH); 20 Oct. 1972, S. Paust 1422 (PERTH); 17 Sep. 2008, K.A. Shepherd & N. Gibson KS 1125 (PERTH).