Botanical name

Acacia eriopoda x tumida var. pilbarensis

Description

Multi-stemmed or spindly and open shrubs 2-3.5 m tall. Bark grey, longitudinally fissured. Branchlets glabrous. Phyllodes narrowly oblong-elliptic to narrowly oblong-oblanceolate, symmetrical or sometimes dimidiate, straight to moderately falcately recurved, narrowed at both ends, 8-13 cm long, (5-) 6-10 mm wide, glabrous, green; parallel longitudinal nerves numerous, fine, with 3-5 nerves slightly raised (when dry) and more evident than the rest (the central nerve the most prominent), minor nerves very close together (to about 0.1 mm apart) and not or scarcely raised; the apex often up-turned, innocuous by a small thickened point; pulvinus about 3 mm long, coarsely transversely wrinkled when dry. Inflorescences predominantly simple but some racemose; raceme axes 1-20 mm long and seemingly growing out at apex into a new shoot; peduncles 1-2 mm long, with sparse to moderately dense, spreading to ąappressed hairs (sub-glabrous when in pod); spikes 15-30 mm long, golden; receptacle glabrous. Flowers 5-merous; calyx shortly dissected, the calyx tube densely hairy. Pods narrowly oblong to sub-moniliform, compressed to sub-terete, slightly raised over and shallowly constricted between seeds, 3-5 cm long, 4-4.5 mm wide, coriaceous, straight to shallowly curved, longitudinally furrowed, glabrous, greyish brown. Seeds longitudinal in pods, obloid-ellipsoid, 4-5 mm long, 2.5-3 mm wide, glossy, dark brown; inner pleurogram 'u'-shaped and about 0.4 mm long, outer pleurogram about 1 mm long; funicle/aril thickened and folded beneath the seed, dull pale yellow when dry (presumably white when fresh).

Characteristic features

Shrubs. Branchlets glabrous. Phyllodes narrowly oblong-elliptic to narrowly oblong-oblanceolate, symmetrical or sometimes dimidiate, straight to moderately falcately recurved, narrowed at both ends (the tip often upturned), 8-13 cm long, mostly 6-10 mm wide, glabrous, finely longitudinally multi-striate with 3-5 nerves more evident than the rest, the minor nerves very close together and the upper and lower margin of equal width. Inflorescences mostly simple but some racemose; spikes 15-30 mm long; peduncles very short (1-2 mm), sub-glabrous (in pod) to moderately densely hairy, the hairs spreading to ąappressed. Pods compressed to sub-terete, coriaceous, slightly raised over and shallowly constricted between seeds, narrow (4-4.5 mm wide), longitudinally furrowed. Seeds with a very small inner pleurogram surrounded by a larger outer one.

Distribution and ecology

A rare putative hybrid confined to the Pilbara region of northwest Western Australia where it is known from only a few populations just north of Nullagine. Both putative parents occurred in one population but only A. eriopoda was found in the other (although A. tumida var. pilbarensis was common in the general area which had been burnt recently). One collector noted that this putative hybrid was also seen at Beatons Gorge, Nullagine. Low rocky hills in light orange-brown sand (pH 8.5), often along drainage lines.

Flowering and fruiting period

Flowering commences in mid-May but it is not known when it ends. Pods with mature seeds have been collected in late October.

Taxonomy

The putative hybrid status of this entity has been determined from field observations and from critical examination of herbarium material. It's phyllodes are intermediate in width between the two putative parents with which it co-occurs in at least only one population. This hybrid is superficially similar to some forms of A. trachycarpa x tumida var. pilbarensis which also occurs north of Nullagine but which is distinguished by having pseudo Minni Ritchi bark. Careful examination (at x10 magnification or higher) of the phyllode margins and nerves is another way of separating these two putative hybrids: in A. eriopoda x tumida var. pilbarensis the upper and lower margins are the same width (observe margins edge-on) and the nerves on the face of the phyllodes are very close together (about 0.1 mm or less apart) whereas in A. trachycarpa x tumida var. pilbarensis the upper margin of the phyllode is clearly broader than the lower margin and the nerves are more widely spaced (about 0.2-0.3 mm apart).

Conservation status

There is insufficient information at present concerning this entity to justify including it on the Department of Environment and Conservation's Declared Rare and Priority Flora List.