Acacia aulacocarpa Cunn. ex Benth., London J. Bot . 1: 378 (1842)
Shrubs 0.5–2 m tall or small trees 2–8 (–15) m tall, single-stemmed or sparingly branched near base, crowns spreading and blue-green. Bark smooth except very shallowly rimose on trunks of largest trees. Branchlets acutely angled for 10–25 cm (occasionally more) below the apex, slender to sub-stout, glabrous. Phyllodes mostly dimidiate to subfalcate, (3–) 5–12.5 cm long, 0.7–3.5 cm wide, glabrous, subglaucous to glaucous with a slight sheen; longitudinal nerves numerous, close (3–4 per mm) and parallel, not anastomosing; pulvinus 4–8 (10) mm long. Inflorescences simple, 1–2 (–4) per axil; peduncles mostly 4–8 mm long, glabrous; spikes 2–5 (–6) cm long, bright golden. Flowers 5-merous; calyx shallowly dissected; ovary densely hairy. Pods 1.5–8 cm long, usually 0.8–1.5 cm wide, straight to shallowly curved, dehiscing along dorsal suture, woody, conspicuously resinous, reddish-brown, prominently nerved, the nerves broad, sharply defined, prominently raised, oblique to longitudinally oblique and sparingly anastomosing. Seeds oblique, ovoid to obloid or ellipsoid, 3.5–5 mm long, 2–3 mm wide; funicle/aril 2–6 mm long (unextended).
Acacia aulacocarpa has a discontinuous distribution along coastal areas and adjoining tablelands of the Great Dividing Range in eastern Qld from the Mt. Windsor Tableland ( c. 25 km east of Daintree), to just south of Brisbane and into northern N.S.W. near Grafton. Recorded also from Qld continental islands of Hinchinbrook, North Keppel and Deloraine (Whitsunday Group) Islands. Despite its extensive distribution it is a relatively uncommon species as populations tend to be locally confined to creek banks or run-on sites near rock outcrops. Flowers Jan. – June
There is considerable variation in habit between some populations, e.g. plants ocurring in coastal areas of North Keppel Island have a compact, domed habit only 0.5 m tall whereas those from along rivers in forests at Finch Hatton Gorge are medium-sized trees to 12 m tall with trunks to 40 cm diameter at breast height. Spindly, sparsely foliaged shrubs 3 m tall with a basal stem diameter of only 1–2.5 cm occur on residual trachyte plugs such as Ngun Ngun (these plants were described by White in 1946 as A. aulacocarpa var. fruticosa ). Plants of a similar habit occur on skeletal soils at Port Clinton, the type locality of A. aulacocarpa . Further discussion of variation is given in McDonald & Maslin (2000), Austral. Syst. Bot . 13: 33–34.
The ‘A. aulacocarpa group’ was recently defined M.W.McDonald and B.R.Maslin, Austral. Syst. Bot. 13: 21-78 (2000), as comprising eight species contained in two subgroups, namely, the A. aulacocarpa subgroup (containing A. aulacocarpa , A. celsa and A. disparrima ) and the A. crassicarpa subgroup (containing A. crassicarpa , A. lamprocarpa , A. midgleyi and A. peregrina ; this last species, together with A. wetarensis , which was provisionally referred to the A. crassicarpa subgroup, occur in New Guinea and Indonesia). Acacia aulacocarpa is distinguished from A. celsa and A. disparrima by its bright golden flower spikes, subglaucous to glaucous phyllodes, densely hairy ovaries and its pods with prominent, oblique to longitudinally oblique nerves. Acacia auriculiformis is sometimes superficially similar to A. aulacocarpa.
Naturally occurring putative hybrids occur with A. celsa (at Paluma Dam) and A. crassicarpa (at Bluewater Creek near Townsville) . Judging from phyllode venation and pod morphology G.N.Batianoff 3484 & C.Dalliston (BRI) from Deloraine Island (Whitsunday Group) also appears to be A. aulacocarpa x A. crassicarpa
Type of accepted name
Lectotype : Port Bowen [= Port Clinton], Queensland, A.Cunningham [specimen not numbered but is actually no. 115, see discussion below] (K, sheet is stamped ‘Herbarium Hookerianum 1867’ and the specimen is in young fruit). Iso-lectotypes : BM (specimen labelled Cunningham 115), K (numbered and unnumbered specimen on a sheet stamped ‘Herbarium Benthamianum 1854’). Para-lectotype : Port Bowen [= Port Clinton], Queensland, A.Cunningham 116 (K - photograph seen, BM: specimens in flower).
Racosperma aulacocarpum (Cunn. ex Benth.) Pedley, Austrobaileya 2: 345 (1987). Type: as for accepted name.
Acacia aulacocarpa var. fruticosa C.T.White, Proc. Roy. Soc. Qd 57: 23 (1946); Racosperma aulacocarpum var. fruticosum (C.T.White) Pedley, Austrobaileya 2: 345 (1987). Type: Ngun Ngun, alt. 800 ft, March 1931, C.T.White 7651; holo: BRI; iso: K, NY.
L.A.J.Thomson, Acacia aulacocarpa, A. cincinnata , A. crassicarpa and A. wetarensis an Annotated Bibliography (CSIRO: Melbourne.), p.9, fig. 1E (1994), pro parte , as to flowering branchlet, as A. aulacocarpa subsp. E; M.W.McDonald & B.R.Maslin, Austral. Syst. Bot. 13(1): 31, fig. 2 & 32, fig. 3 (2000).
Qld: Deloraine Island headland, G.N.Batianoff 3517 & C.Dalliston (BRI); Carrington Falls, 8 km SSE of Atherton, J.R.Clarkson 9712 (BRI, DNA, K, L, MBA, NSW, PERTH); Paluma Dam, NW of Paluma, M.W.McDonald 2171 & P.A.Butcher (BRI, CANB, K, NSW, PERTH); 5.7 km W of Herberton along road to Irvinebank, M.W.McDonald 2363 & P.A.Butcher (BRI, CANB, NSW, PERTH); Ngunngun, c. 2 km west of Glass House Mountains township, M.W.McDonald & B.R.Maslin BRM 7612 (BRI, CANB, DNA, K, NSW, NY, PERTH); Port Clinton, base of Mt. Flinders (on NNW side), c. 60 km due north of Yeppoon, M.W.McDonald & B.R.Maslin BRM 7615 (BRI, PERTH); Finch Hatton Gorge, c. 45 km due W of Mackay, M.W.McDonald & B.R.Maslin BRM 7624 (BRI, CANB, NSW, PERTH). N.S.W.: Fortis Creek State Forest, P.Richards 658 & R.Armstrong (CANB, NSW).
The above description is abstracted from the treatment provided by M.W.McDonald & B.R.Maslin (2000), Austral. Syst. Bot . 13: 29–34.