Triodia avenoides

Name

Triodia avenoides M.D.Barrett, ined.

Citation

Nuytsia, in press, (2017)

Derivation

avenoides— from the Latin avena (wild oat) and –oides (Greek adjectival suffix indicating similarity), in reference to the similarity of the open inflorescence, especially when the glumes are empty, to the Common Oat, Avena sativa.

Common name

Western Feathertop Spinifex

Synonyms

None

Diagnostic features

Foliage resinous; leaf sheath surfaces glabrous; leaf blades epistomatous (soft-type); orifice hairs straight to tangled; lower glume narrowly lanceolate, L:W>6, 12.5–32 mm long, (2.1–)2.2–3.6 mm wide; lemmas 3-awned, bitextured, the lower indurated part uniformly covered with ±appressed hairs; lemma body 1.4–1.8 mm wide; callus sharply pungent, 0.8–1 mm long; palea bitextured, lacking hairs; on dunes and sand plains in the Carnarvon bioregion and immediately adjacent parts of other sub-regions in the west Pilbara.

Habitat

Occurs on red sand dunes or on deep red sand plains

Distribution and frequency

Endemic to the sands of the Carnarvon Basin in the west Pilbara and Carnarvon bioregions, where it is widespread but patchy

Similar species

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

Most similar to T. schinzii, sharing the narrowly lanceolate glumes, 3-awned and bitextured lemmas, and sharply acute callus ≥0.8 mm long. Triodia avenoides differs from T. schinzii in having lemma body 1.3–1.8 mm wide (0.8–1.25 mm wide in T. schinzii), broader glumes (2.1–)2.2–3.6 mm wide [1.5–2.1(–2.2) mm wide in T. schinzii], 2–3 spikelets on the longest (basal) panicle branches (3–5 spikelets in T. schinzii), and a non-overlapping distribution. Triodia avenoides occurs on sands of the Carnarvon Basin west of the Pilbara, while T. schinzii occurs to north and east, on sands of the Dampierland, Great Sandy Desert and Little Sandy Desert, extending into the Pilbara on sand plains between Port Hedland and Karratha, in patches in the eastern Chichester west to Abydos and Woodstock stations, and along the Fortescue Valley east of Munjina (Auski).

Several species sharing awned lemmas and bitextured lemma body occur in the Pilbara. Other than T. schinzii discussed above, all occur on rocky substrates. Triodia basitricha differs in having smaller glumes, and hairs on the surface of the leaf sheaths (glabrous in T. avenoides).

Triodia sp. Mt Ella differs in having a hairy palea, shorter glumes ≤12.5 mm long and a shorter callus ≤0.7 mm long (palea glabrous, glumes ≥15 mm, callus long-pungent and ≥0.8 mm in T. avenoides).

Triodia degreyensis differs in having a hairy palea, generally shorter glumes 12.4–17 mm long and a shorter callus <0.5 mm long (palea glabrous, glumes 12.5–32 mm long, callus long-pungent and ≥0.8 mm in T. avenoides), as well as occurring on a rocky substrate and a disjunct distribution.

Conservation status

Not considered at risk.

Identification without florets

The only other species with either resinous foliage or epistomatous leaves in the West Pilbara is T. epactia, which has much shorter and broader glumes (L:W4) and lacks lemma awns.

Variation

A relatively uniform species.

Notes

Triodia avenoides was treated as part of T. schinzii by Lazarides (1997), Lazarides et al. (2005) and Ausgrass (Sharp & Simon, 2002; Simon & Alonso, 2014). A full description can be found in Barrett (2017b).

Probably palatable to stock when young.