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Photographer: B.R. Maslin
, BRM 6272, ORIGINAL SCAN, ADJUSTED RICHARD WOODMAN.jpg)
Spiny stipules on stem (phyllodes have fallen). Photographer: B.R. Maslin
, phyllodes glaucous, E of Newman, 10 Aug 2006, BRM ADJUSTED BY J. FIELD.jpg)
Photographer: B.R. Maslin
Photographer: J. Maslin
Photographer: B.R. Maslin
Photographer: M.W. McDonald
, E Scott s.n., lab photo by Fiona McCallum ADJUSTED.jpg)
Seed from one herbarium voucher. Scale in mm. Photographer: F. McCallum.
Botanical name
Acacia synchronicia Maslin, Nuytsia 8: 302, figs 6A-K (1992)
Common name
Bardi Bush (in the past this name had sometimes been applied to A. victoriae , Elegant Wattle), Bramble Wattle and Prickly Acacia
Aboriginal name
Nhurungan, Nurungan or Ghurungan (Kurrama), Nhurrungan (Banjyima), Thambarli (Thalanyji), Purtartu, Pana-Pana or Kupi (Nyangumarta) and Jilkuru (Kariyarra)
Description
Spreading, somewhat straggly, openly branched, glabrous shrubs or small trees 1.5-4 (-6) m tall, with few to numerous main stems from the base. Bark grey and finely longitudinally fissured at base of main stems otherwise smooth, the upper branches commonly bronze but ranging to greenish bronze, light brown, orange or yellowish green, white pruinose throughout on young plants. Branchlets grey to light brown or greenish at extremities, often lightly or conspicuously pruinose. New shoots pale green, thin-textured. Stipules spiny, present on young plants but frequently absent or few on mature plants, slender, 3-10 mm long. Phyllodes elliptic to narrowly elliptic or oblong-oblanceolate, infrequently narrowly oblong, mostly 15-25 (-35) mm long, 3-7 mm wide, l:w = 3-7, smooth and thin-textured or sub-fleshy when fresh, smooth or finely wrinkled when dry, glaucous to sub-glaucous , grey-green or silvery grey (pale green on new shoots); midrib normally visible but not overly prominent when dry, occasionally (when phyllodes very narrow) superficially absent, finely penninerved with the minor nerves anastomosing or occasionally (when phyllodes very narrow) superficially absent; apices rounded-obtuse or rarely acute, mucronulate with central or excentric mucro, innocuous. Gland rather prominent, situated on upper margin of phyllode 0-2 mm above pulvinus, normally 0.7-1.3 mm long and 0.5-1 mm wide. Inflorescences simple, initiated on new shoots with 1 or 2 peduncles arising within axil of developing phyllodes, subtending phyllodes fully develop before heads reach anthesis, short racemes rare; peduncles 9-15 (-20) mm long; heads globular, about 8 mm in diameter when fresh, light golden, with 40-70 flowers. Flowers 5-merous; sepals free, linear-spathulate; petals nerveless. Pods oblong to narrowly oblong, flat but rounded over seeds along midline, mostly straight-edged, 2-5 (-6) cm long, (8-) 9-12 mm wide, papery, straight to slightly curved. Seeds transverse in the pods, ovoid to ellipsoid or obloid-ellipsoid, 4-5 mm long, somewhat compressed, not or slightly shiny, mottled black and either yellow or light brown; areole "u"-shaped and very small at centre of seed; funicle short, thick, cream coloured, slightly expanded into a small terminal aril.
Characteristic features
Somewhat straggly, openly branched shrubs or small trees, upper branches commonly bronze-coloured. Branchlets sometimes pruinose. Stipules spiny, present on young plants but frequently absent or few on mature plants. Phyllodes mostly elliptic to narrowly elliptic or oblong-oblanceolate, relatively short and narrow (mostly 15-25 x 3-7 mm with l:w = 3-7), glaucous to sub-glaucous, grey-green or silvery grey, sub-fleshy (sometimes finely wrinkled with midrib normally visible but not prominent when dry); basal gland rather prominent. Inflorescences simple, initiated on new shoots with 1 or 2 peduncles within axil of developing phyllodes, subtending phyllodes fully develop before heads reach anthesis; heads light golden, 40-70-flowered. Pods oblong to narrowly oblong, papery, flat but rounded over seeds along midline, mostly straight -edged. Seeds transverse, mottled black and either yellow or light brown, aril small.
Distribution and ecology
Occurs in northwest Western Australia where it extends from Shark Bay north to near De Grey Station and east to the Rudall River National Park. It is also found in the southern Kimberley region (extending into Northern Territory) and is scattered in Murchison district (Cue - Yalgoo area) south of the Pilbara. Acacia synchronicia is widespread and scattered throughout the Pilbara but because it is generally confined to watercourses and alluvial flats (in loam or clay soils) it shows a discontinuous distribution pattern. In some areas it is particularly common in the places where it occurs and is sometimes regarded by pastoralists as a troublesome native woody weed or increaser (see discussion below under Notes).
Flowering and fruiting period
Pilbara plants flower mostly between September and December with the main flush in October-November; in the Kimberley region, however, flowering may commence as early as June or July. Pods with mature seeds have been collected in late October, December and January but outside the Pilbara they have also been found in April, May and November.
Variation
The phyllodes of A. synchronicia vary considerably in shape and size, particularly in their width. The above description applies to specimens regarded as 'typical' of the species. Specimens with broader than normal phyllodes sometimes co-occur with typical form and are treated here as A. synchronicia (broad phyllode variant). Specimens with very narrow phyllodes that were formerly referred to A. synchronicia are now called A. robeorum.
Taxonomy
Acacia synchronicia is a member of the 'A. victoriae group' of species (see Maslin 1992 for discussion); other members of this group which occur in the Pilbara include A. aphanoclada, A. cuspidifolia, A. glaucocaesia, A. robeorum and A. victoriae. It is most closely related to A. robeorum (see that species for discussion). In the past A. synchronicia had been confused with A. victoriae which is distinguished by its pale-coloured, fewer-flowered heads which are mostly arranged in short racemes, globose seeds and non-fleshy phyllodes with a more prominent midrib. The two species co-occur on Mt Florance Station, north of Wittenoom. Near Cleaverville (between Karratha and Roebourne) A. synchronicia co-occurs with A. glaucocaesia which has much wider, thin-textured phyllodes and paler-coloured heads arranged in short racemes; putative hybrids occur between the two species at this locality.
Notes
This species regenerates well from seed, a feature that may be attributed to the relatively high germination rate (15%), even without pretreatment to break dormancy (Fox and Dunlop 1983).
In most instances the presence of A. synchronicia is of little value in respect to pasture condition, however, it is considered an undesirable species when it increases on perennial grass pasture systems (Payne and Mitchell 2002). Under such circumstances Bardi Bush becomes a noteworthy nuisance plant and has been labeled a woody weed in some instances (e.g. Fortescue River floodplain on Ethel Creek Station, Jamindie hardpan stony plains on Roy Hill Station and parts of Mt Florance Station). The extent of the increase can be severe resulting in the formation of dense thickets which are impenetrable to livestock and significantly impinge on mustering activities. Beard (1975) noted that this increase in A. synchronicia was occurring at the expense of Mulga in the Fortescue Valley back in the early 1970s. The extent of Bardi Bush increase in some areas has resulted in the use of chemical and mechanical controls to open up paddocks thereby facilitating livestock grazing and mustering operations. In some situations it has been suggested that Bardi Bush may be acting in a facilitation role providing safe sites for the re-establishment of desirable perennial grasses (e.g. Mitchell grass, ribbon grass) on degraded lands. Indeed, Fox and Davies (1983) identified this species as having potential for the rehabilitation of degraded pastoral areas south of the Pilbara and Tyler (1988) notes that it is somewhat salt-tolerant. It is possible that at least some of the information presented under A. victoriae by Mitchell and Wilcox (1994) refers to A. synchronicia.
Livestock readily eat the flowers, immature pods and browse the foliage of young Bardi Bush.
Indigenous people ate immature pods and harvested seeds for flour to use in dampers and collected sweet gum from cracks in the branches and main trunk. They harvested edible grubs (nargarla) from the roots and lerp (marrajun) from the phyllodes. Phyllodes were collected and boiled in water to make a wash to treat boils and a tonic that acted as a diuretic (pass urine).
Conservation status
Not considered rare of endangered.
Origin of name
The botanical name refers to the synchronous initiation of phyllodes and inflorescences on new shoots.
References
Beard, J.S. (1975). Vegetation survey of Western Australia - Pilbara. (University of Western Australia Press: Nedlands.)
Fox, J.E.D. and Davies, G. (1982). Establishment of Acacia victoriae germination and early growth. pp. 31-39. Mulga Research Centre. Annual Report 1982 pp. 107. (Western Australian Institute of Technology: Bentley.)
Fox, J.E.D. and Dunlop, J.N. (1983). Acacia species of the Hamersley Ranges, Pilbara Region of Western Australia. Mulga Research Centre. Occasional Report No. 3. pp. 94. (Western Australian Institute of Technology: Bentley.)
Maslin, B.R. (1992). Acacia Miscellany 6. A review of Acacia victoriae and related species (Leguminosae: Mimosoideae: Section Phyllodineae). Nuytsia 8: 285-309.
Mitchell, A.A. and Wilcox, D.G. (1994). Arid shrubland plants of Western Australia. Edn. 2. pp. 478. (University of Western Australia Press in association with the Department of Agriculture: Perth.)
Payne, A.L. and Mitchell, A.A. (2002). Pasture Condition guides for the Pilbara. pp. 83. (Department of Agriculture: South Perth.)
Tyler, J.P. (1998). The Dampier Salt Guide to Pilbara Plants for the Garden. pp. 148. (Dampier Salt (Operations): Karratha.)