Name

Triodia basitricha M.D.Barrett

Citation

Nuytsia 26:71–73 (2015)

Derivation

basitricha — from the (transliterated) Greek basis, base, and trichos, hair, in reference to the hairy leaf sheaths.

Common name

Pilbara Curly Spinifex

Synonyms

Triodia sp. Millstream (A.A. Mitchell PRP 207)

Diagnostic features

Foliage non-resinous to moderately resinous; leaf sheath surfaces with sparse to moderately dense hairs; leaf blades epistomatous (soft-type); lower glume narrowly lanceolate, L:W>5, 10–12.5 mm long; lemmas 3-awned, bitextured, the lower part uniformly covered with ±appressed hairs; callus acute but not sharply pungent, <0.5 mm long; palea bitextured, hairy; on rocky or gravelly slopes of mountains or low hills.

Habitat

Occurs on rocky and gravelly slopes of mountains or low hills.

Distribution and frequency

Endemic to the Pilbara and surrounds. Very patchily distributed throughout the Chichester and western Hamersley sub-regions, with an isolated occurrence in the Barlee Range south of the Pilbara. Very patchy throughout most of its range, but locally extensive north of Tom Price, in the vicinity of Brockman mines and Coolawanyah Station.

Similar species

Triodia basitricha belongs to the Soft group, sharing the epistomatous (soft-type) leaf blades.

The combination of epistomatous (soft-type) leaves and presence of hairs on the surfaces of the leaf sheaths is found only in a few other species: T. karijini, T. pisoliticola and T. veniciae. Amongst these, only T. basitricha has bitextured lemmas at maturity.

Several other species share with T. basitricha the awned, bitextured lemmas: T. degreyensis, T. avenoides, T. sp. Mt Ella, and T. schinzii. Triodia basitricha is the only one of these species with (sparse to moderately dense) hairs on the leaf sheath surface. Triodia avenoides and T. schinzii have a sharply pungent callus 0.8–1.5 mm long (0.2–0.5 mm long and blunt to acute and usually not sharply pungent in the remaining species). Triodia sp. Mt Ella is always strongly resinous (non-resinous to weakly resinous in T. basitricha). Triodia degreyensis has longer glumes (12.4–17 mm long) than T. basitricha (10–12.5 mm long).

Conservation status

Priority Three.

Identification without florets

Only three other species share a combination of epistomatous (soft-type) leaves and hairy leaf sheath surfaces, T. karijini, T. veniciae, and T. pisoliticola. None of these species are known to occur within the distribution of T. basitricha s.s., however both T. basitricha and T. veniciae occur in the eastern Chichester sub-region, and might possibly co-occur. Triodia basitricha has longer lower glumes 10–12.5 mm long (5.4–8.5 mm long in T. veniciae) and 4–5 spikelets on longest basal branches (7–14 in T. veniciae).

Variation

The leaf sheath surfaces are variably hairy, from very sparse to moderately dense.

A population from near Pannawonica (P.J. Davidson 2026, CANB) lacks hairs on the surface of the leaf sheaths, and are genetically close to T. basitricha. The taxonomic status of these plants remains to be determined, and it is not treated in the key.

Notes

Triodia basitricha was mapped under T. melvillei and T. schinzii by Lazarides (1997), Lazarides et al. (2005) and Ausgrass (Sharp & Simon, 2002; Simon & Alonso, 2014), but their descriptions did not cover T. basitricha.

A full description of T. basitricha can be found in Barrett & Barrett (2015).