Acacia brachybotrya

Acacia brachybotrya Benth., London J. Bot. 1: 347 (1842)

Grey Mulga , Grey Wattle

Dense, round, spreading shrub 1–3 m high. Branchlets variably hairy, sometimes glabrous. New shoots rarely golden-hairy. Phyllodes variable, normally slightly asymmetrically oblong-elliptic to oblong-obovate (but frequently narrowly so) or obovate to oblanceolate, usually 1–3 cm long and 4–13 mm wide with l:w = 1.5–3.5, obtuse to subacute, grey-green to glaucous, with indumentum similar to branchlets, sometimes glabrous, 1-nerved per face; lateral nerves not prominent. Inflorescences 1–6-headed racemes; raceme axes 0.5–5 mm long, hairy, sometimes glabrous; peduncles 4–15 mm long, slender, hairy, sometimes glabrous; heads globular, 18–30-flowered, golden. Flowers 5-merous; sepals variably united. Pods linear to narrowly oblong, to 9 cm long, 4–8 mm wide, firmly chartaceous to coriaceous, dark brown or black, lightly pruinose, glabrous or hairy. Seeds longitudinal, 4–5.5 mm long, subshiny, brown to black, punctate about centre, arillate.

Widely distributed in semi-arid areas of S.E. Australia from Yalata, S.A., E to near Bendigo, Vic. and N to Nymagee, N.S.W. Occurs on a variety of soils, often in mallee communities. The Qld record of A. brachybotrya by L.Pedley, Contr. Queensland Herb. 4: 6 (1969), is A. victoriae subsp. arida .

G.J.Leach & T.Wiffen, Bot. J. Linn. Soc. 76: 53–69 (1978), have shown A. x grayana to be a hybrid between A. brachybotrya and A. calamifolia (the latter parent is now known to be A. euthycarpa ).

Occasionally confused with A. decora (which has much longer racemes and appressed-puberulous peduncles) or A. buxifolia .

Very polymorphic and as circumscribed here probably comprises more than one taxon. Indumentum characters are important in discriminating the three main variants which can be recognised. Much work is needed to clarify the relationship between these variants because intermediates appear to occur. Although A. argyrophylla and A. spilleriana are treated as distinct species they may ultimately prove better placed within A. brachybotrya .

Acacia brachybotrya Benth. (typical variant)

The first main variant has indumentum hairs that are ±straight and patent, sometimes absent, and phyllodes 10–30 mm long. It occurs in N.S.W., Vic. and S.A. (to the Murray R.) and includes the types of A. brachybotrya , A. brachybotrya forma glabra and Mueller’s undated ‘Mallee scrub’ syntype of A. dictyocarpa  (sheet stamped Herb. Hookerianum). When the indumentum is dense, this variant may resemble A. spilleriana .

Acacia brachybotrya Benth. (appressed-hair variant)

The second variant has indumentum hairs that are straight, appressed and sparse to dense, silvery or golden on new shoots, and phyllodes 8–30 mm long, rarely to 40 mm. It occurs from the Wimmera region (western Vic.) to Yalata, NW of the Eyre Penin., S.A. and includes Mueller’s Oct. 1848 ‘Murray scrub’ syntype of A. dictyocarpa (sheet stamped Herb. Benthamianum). Specimens with golden new shoots may resemble A. argyrophylla and in some cases hybridity is suspected. Acacia semiaurea may be a hybrid involving A. retinodes and either A. argyrophylla or this variant of A. brachybotrya .

Acacia brachybotrya Benth. (Wirrabara variant)

The third variant has indumentum hairs that are ±subappressed and antrorsely hooked to subcrisped, and phyllodes 9–30 mm long. It occurs in S.A. from Bute to Burra and Wirrabara and encompasses, in part, J.E.Brown’s concept of A. spilleriana . The flowering branch on MEL615097 is this variant and is possibly an isosyntype of A. spilleriana ; the detached pods accompanying this specimen may not belong to this taxon as they are 12–14 mm wide and have oblique seeds. The specimens were unnamed and without locality but J.E.Brown was given as collector.

Type of accepted name

Peel’s Ra., [= Cocoparra Ra.], N.S.W., A.Cunningham s.n .; syn: K; Peel’s Ra. [= Cocoparra Ra.], N.S.W., May and June 1817, A.Cunningham 416 ; syn: K, NSW.

Synonymy

Acacia brachybotrya is based on the following: Acacia brachybotrya f. glaucophylla Benth., Fl. Austral. 2: 374 (1864), nom. illeg. (includes type of A. brachybotrya ); A. brachybotrya var. glaucophylla Maiden, Wattles & Wattle-barks 3rd edn, 60, 67 (1906), nom. illeg. (includes type of A. brachybotrya ). Type: as for accepted name.

Acacia dictyocarpa Benth., Linnaea 26: 616 (1855). Type: Murray scrub [apparently that part of the Murray Mallee, S.A., S of the modern Truro - Blanchtown Hwy, towards The Marne R., fide D.K.Kraehenbuehl, J. Adelaide Bot. Gard. 3: 111, 1981], Oct. 1848, F.Mueller s.n. ; syn: K (sheet stamped Herb. Benthamianum); Mallee scrub [presumably the Murray Mallee, S.A., see preceding syntype], without date, F.Mueller s.n. ; syn: K (sheet stamped Herb. Hookerianum); ?isosyn: MEL615106.

Acacia brachybotrya f. glabra Benth., Fl. Austral. 2: 374 (1864); A. brachybotrya var. glabra (Benth.) J.H.Maiden, Wattles & Wattle-barks 3rd edn, 60, 67 (1906). Type: Wimmera, Vic., J.Dallachy ; ?holo: K; ?iso MEL.

Acacia argyrophylla F.Muell.: see Doubtful names.

Illustrations

G.M.Cunningham et al. , Pl. W New South Wales 354 (1981), both right-hand plates (the lowermost plate erroneously labelled A. buxifolia ); L.F.Costermans, Native Trees & Shrubs SE Australia 311 (1981); T.Tame, Acacias SE Australia 120, fig. 124, pl. 124a (1992); D.J.E.Whibley & D.E.Symon, Acacias S. Australia 2nd edn, 67 (1992).

Representative collections

S.A.: 17 km SSE of Yalata on dog fence, B.Copley 2631 (AD); Wirrabara Forest, c. 10 km due SW of Wirrabara township, B.R.Maslin 5999 (AD, K, MEL, PERTH) and 6000 (CANB, NSW, PERTH). N.S.W.: E of Bungooney, L. Cargelligo, P.L. Milthorpe 5240 & G.M.Cunningham (NSW, PERTH); 17 km S of Kaleentha Loop, J.Pickard 2578 (NSW). Vic.: 25.2 km E of Nhill on Western Hwy, N.Hall H80/107 (MEL, NSW).

(BRM)

The information presented here originally appeared on the WATTLE CD-ROM which was jointly published by the Australian Biological Resources Study, Canberra, and the Department of Parks and Wildlife, Perth; it was produced by CSIRO Publishing from where it is available for purchase. The WATTLE custodians are thanked for allowing us to post this information here.

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