Botanical name

Acacia sp. Jimblebar (S. van Leeuwen 1342)

Description

Trees to 3 m tall. Branchlets glabrous. New shoots resinous, dark coloured and not sticky when dry. Phyllodes narrowly oblong-oblanceolate, narrowed towards the base, 5-9 cm long, 4-8 mm wide, mostly straight, some slightly incurved or slightly recurved, ascending to erect, green, glabrous or with microscopic appressed hairs between the nerves; parallel longitudinal nerves numerous, fine and close together, central nerve more pronounced than the rest and normally with a sub-prominent nerve on either side and parallel to it, the minor nerves close together with a few longitudinally anastomosing; apices obtuse-mucronate, innocuous. Gland on upper margin of phyllode 0-1 mm above pulvinus. Inflorescences simple or rudimentary racemes 1-3 mm long, 1 or 2 within axil of phyllodes; peduncles mostly 15-25 mm long (a few atypically shorter), about as long or longer than the spikes, resinous, glabrous or with microscopic, fine, wide-spreading hairs; receptacle with microscopic, fine, wide-spreading hairs; spikes 10-20 mm long, the flowers sub- densely arranged within the spikes. Flowers 5-merous; calyx ˝-ž length of corolla, very shortly dissected into broadly triangular lobes, glabrous; petals glabrous, prominently 1-nerved when dry. Pods and seeds not seen.

Characteristic features

Branchlets glabrous. New shoots resinous, dark coloured when dry. Phyllodes narrowly oblong-oblanceolate, narrowed towards the base, mostly straight, ascending to erect; parallel longitudinal nerves numerous, central nerve the most pronounced, minor nerves close together with a few longitudinally anastomosing; apices obtuse-mucronate. Inflorescences simple or rudimentary racemes; spikes with flowers sub- densely arranged; peduncles long (mostly 15-25 mm), about as long or longer than the spikes, resinous; receptacle with microscopic, fine, wide-spreading hairs. Pods and seeds not seen.

Distribution and ecology

Confined to the Pilbara region of northwest Western Australia where it is known only from the Jimblebar Mine Road near Shovelanna Hill, about 30 km due east of Newman. It is uncommon in the places where it occurs. Grows high in the landscape (southern aspect) on gentle detrital slope in gravelly red loam. Associated acacias include A. adsurgens, A. ancistrocarpa, A. aneura, A. bivenosa, A. monticola, A. sibirica and A. tetragonophylla.

Flowering and fruiting period

Flowering commences in early July and probably extends to about the end of September. Pods have not been seen.

Taxonomy

The taxonomic status of this entity is uncertain. The long peduncles which are about as long, or longer, than the spikes are reminiscent of A. adsurgens (with which it grows). However, A. adsurgens is distinguished by its linear phyllodes which are normally longer and narrower, shorter peduncles, and flowers which are more densely arranged within the spikes. It is possible that Acacia sp. Jimblebar (S. van Leeuwen 1342) represents a hybrid with A. adsurgens as one of the parents.

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.

Origin of name

The phrase name Acacia sp. Jimblebar (S. van Leeuwen 1342) identifies this taxon at the W.A. Herbarium.