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Botanical name

Common name

Aboriginal name

Description

Characteristic features

Distribution and ecology

Flowering and fruiting period

Variation

Taxonomy

Affinities

Notes

Conservation status

Origin of name

References

Acacia tumida var. pilbarensis

Botanical name

Acacia tumida var. pilbarensis M.W. McDonald, Austral. Syst. Bot. 16: 162, fig. 7 (2003)

Common name

Pilbara Pindan Wattle (preferred common name) and Silver-leaf Wattle

Aboriginal name

Muwarlingu (Yindjibarndi), Mugarli or Moogali (Ngarluma), Mukarti, Mukarli or Pulpa (Nyangumarta) and Pilamurka, Billamurga or Bilamurga (Kurrama)

Description

Shapely, erect, often 'v'-shaped, openly branched shrubs or trees (1-) 2-6 m tall, crown dense or sub-dense, single-stemmed or branching near base into a number of main stems. Bark usually smooth and pruinose on stems of young and adolescent plants and the upper branches of mature plants, becoming grey, longitudinally fissured and fibrous on trunks of mature plants. Branchlets glabrous (except loosely pilose on very young plants), pruinose or sometimes pruinosity absent revealing an orange or light brown undersurface. New shoots with a dense layer of rusty brown, microscopic resin-hairs when first initiated (indumentum soon lost). Phyllodes large, 8-15 cm long, straight, dimidiate and broad (to 40 mm wide) on young and adolescent plants, becoming shallowly or strongly falcate and narrower (8-22 mm wide) on mature plants, thinly coriaceous, wide-spreading, glabrous (except loosely pilose on seedling plants), glaucous (especially on young plants) to sub-glaucous or dull mid-green, non-pruinose or lightly pruinose; longitudinal nerves numerous, fine and close together, few anastomoses often present, 3 rather prominent and 3 or 4 less prominent nerves more evident than the rest; narrowed towards the non-spiny apex; pulvinus 4-10 mm long. Gland not prominent, located on upper margin of phyllode at distal end of pulvinus. Inflorescences axillary or terminal racemes which sometimes form panicles; peduncles (3-) 4-10 (-12) mm long, glabrous; spikes showy, fragrant, 20-40 (-60) mm long, yellow to light golden, the flowers densely arranged. Flowers 5-merous; calyx small, deeply dissected. Pods generally pendulous, narrowly oblong, terete to sub-terete or sometimes flattened, sometimes slightly to moderately constricted between and over seeds, 3.5-12 cm long, (5-) 6-10 (-12) mm wide, coriaceous-crustaceous (could be misinterpreted as sub-woody), normally sub-straight to (irregularly) shallowly curved, occasionally strongly curved into an open semicircle, finely longitudinally wrinkled, glabrous, not resinous but emitting a 'resinous' fragrance, light greyish brown or yellow-brown, usually lightly to moderately pruinose but sometimes pruinosity absent. Seeds obliquely placed in pods, obloid to ellipsoid, 5-7 mm long, 3-5 mm wide, black, glossy except slightly less shiny at centre of the seed (i.e. the areole and a band external to the pleurogram); aril folded and creamy.

Characteristic features

Shapely shrubs or trees mostly 2-6 m tall, single- or multi-stemmed. Bark usually smooth and pruinose on stems of young and adolescent plants and the upper branches of mature plants, becoming grey, longitudinally fissured and fibrous on trunks of mature plants. Branchlets glabrous, usually pruinose. Phyllodes large, 8-15 cm long, straight, dimidiate and broad (to 40 mm wide) on young and adolescent plants, becoming shallowly or strongly falcate and narrower (8-22 mm wide) on mature plants, glaucous (especially on young plants) to sub-glaucous or dull mid-green, glabrous (except loosely pilose when very young); finely longitudinal multi-striate with some nerves more evident than the rest, nerves mostly parallel but few anastomoses often present. Inflorescences axillary or terminal open racemes; peduncles glabrous, often pruinose; spikes showy, yellow to light golden, showy. Pods narrowly oblong, terete to sub-terete or flattened, coriaceous-crustaceous (could be misinterpreted as sub-woody), finely longitudinally wrinkled, light greyish brown or yellow-brown, usually lightly to moderately pruinose, not resinous but emitting a 'resinous' fragrance. Seeds black, glossy; aril creamy.

Distribution and ecology

Largely confined to the Pilbara region in northwest Western Australia with scattered occurrence in the Little and Great Sandy Deserts in the vicinity of Telfer. In the Pilbara it is common in many places, mostly north of the Hamersley Range, especially in the Fortescue Valley and on the pindan plain north of Whim Creek and the sandy coastal plains south of the Fortescue Roadhouse. In some areas it forms localized populations where it shows prolific germination from seed following fire and other disturbance (e.g. along road verges). This variety grows mainly in open woodlands often along seasonal creeks and drainage lines in neutral to alkaline sand (pH 6-7) or clay loam (pH 8-9) plains or in rocky hills.

Flowering and fruiting period

Some plants have been recorded as flowering from April to September but the main flush is from late May to July. Pods with mature seeds have been collected between September and December with most occurring from late October to early November.

Variation

Phyllodes on juvenile and adolescent plants are broader than those found on mature adults (which are developed when plants are about 2 years of age). Although the seedling phyllodes are invested with dense, spreading hairs, the indumentum is lost by the time plants reach adolescence (at about 6-12 months of age).

Taxonomy

Acacia tumida comprises four varieties (see McDonald 2003) of which var. pilbarensis and var. kulparn occur naturally in the Pilbara; the former is by far the more common in the region (see var. kulparn for discussion). Variety tumida is also likely to have been introduced to the Pilbara (see under Notes below). It is often hard to distinguish var. tumida from var. pilbarensis but McDonald (2003) reports that the former grows to a larger tree (to 15 m tall) and has adult phyllodes that are generally broader (1.5-6 cm wide), more falcate and less pruinose than those of var. pilbarensis.

Affinities

Acacia hamersleyensis is superficially similar to var. pilbarensis but differs most readily in having generally straighter phyllodes, simple (not racemose) inflorescences, broader spikes and hairy pods. Acacia tumida var. pilbarensis may also superficially resemble A. fecunda (see that species for distinguishing features). Within the Pilbara region var. pilbarensis seems to occasionally hybridize with A. eriopoda (see A. eriopoda x tumida var. pilbarensis), A. monticola (see A. monticola x tumida var. pilbarensis) and A. trachycarpa (see A. trachycarpa x tumida var. pilbarensis), and possibly hybridizes with A. citrinoviridis (see A.? citrinoviridis x tumida var. pilbarensis). From a distance sterile plants of var. pilbarensis can be mistaken for a species of eucalypt.

Notes

This variety is fire-sensitive and does not coppice following fire (McDonald et al. 1998; McDonald 2003).

This is an attractive variety that would be well-suited for amenity and garden planting in arid areas on account of its long, showy spikes and (at least when young) stems, however plants are rather short-lived and can become straggly and untidy with age.

As reported by Juluwarlu Aboriginal Corporation (2003) indigenous peoples of the Pilbara used var. pilbarensis as a food. The seeds were put in a yandi (dish) with a yawan (hot cooking stone), shaken around until cooked and then eaten. Also, the roots of this plant are a source of edible bardi grubs. The straight stems were used in spear making.

This variety is used extensive in the mine site rehabilitation industry in the Pilbara and elsewhere in northern Australia. It is likely that var. tumida also occurs in the Pilbara on some rehabilitated mine sites; significant volumes of seed of A. tumida was obtained from Queensland and Northern Territory for rehabilitation of Pilbara mine sites in the late 1970s and 1980 (before issues of provenance were enforced by regulatory authorities) and it is likely that this seed came from plants of var. tumida.

Conservation status

Not considered rare or endangered.

Origin of name

The botanical name comes from the Latin tumida (swollen). Ferdinand von Mueller, who first described the species, did not indicate the reason for the name, but the type material shows terete pods which may account for his use of this name. The varietal name refers to the Pilbara region where this variety predominates.

References

Juluwarlu Aboriginal Corporation (2003). Wanggalili: Yindjibarndi and Ngarluma Plants. pp. 128. (Juluwarlu Aboriginal Corporation: Roebourne, Western Australia.)

McDonald, M.W. (2003). Revision of Acacia tumida (Leguminosae: Mimosoideae) and close allies, including description of three rare taxa. Australian Systematic Botany 16: 139-164.

McDonald, M.W., Harwood, C.E. and Whitfeld, S.J. (1998). Morphological variation in Acacia tumida and implications for its utilisation. pp. 341-346. In: J.W. Turnbull, H.R. Crompton and K. Pinyopursarerk (eds) Recent developments in Acacia planting. Proceedings of an international workshop held in Hanoi, Vietnam, 27-30 October 1997. ACIAR Proceedings No. 82. pp. 383. (Australian Centre for International Agricultural Research: Canberra.)