Thelepogon australiensis

Botanical Description

An annual species, culms erect, 70-140 cm tall, recorded as red in colour particularly towards the base. Leaves cauline, leaf sheaths and blades hairy, blades 5-12 cm long, 6-10 mm wide. Inflorescence a jointed raceme, with 1-3 racemes per culm, if more than one raceme present racemes arranged digitately (branching like the fingers of a hand) (Fig. 2). Racemes are 2.5-5.5 mm long with 10-13 joints, the raceme fragile at the joints (nodes). Each segment of the raceme has a sessile spikelet and a naked pedicel, in this genus this pedicel is all that remains of what is considered the companion or pedicelled spikelet, there are no spikelet parts present (Fig. 5a & b). The glumes of the sessile spikelet are dissimilar, the lower glume hardened, c. 6.5 mm long, glabrous but roughly warty or scarbrid on the edges (Figs. 4a & b). Sessile spikelets are bisexual, the lower floret male and the upper floret bisexual, the lemma of upper floret is bilobed to 2/3 of the length with the bent, twisted awn arising between the lobes, awn 16 mm long.

Figure 1. Herbarium sheet of Thelepogon australiensis (MBA7155) Figure 2. Thelepogon australiensis inflorescence (MBA7155)

Diagnostic Features
This species could be easily confused with Sehima nervosum and species of Ischaemum, especially if only one raceme is produced, both are very common grasses across Cape York Peninsula. Thelepogon can be distinguished by careful examination of the spikelets with a hand lens or dissecting microscope. Sehima and Ischaemum have spikelets in pairs along each segment or internode of the raceme, the pairs are comprised of a sessile spikelet and a pedicelled spikelet (often referred to as the companion spikelet). In Sehima nervosum the companion spikelet is well developed (Fig. 6a) and in Ischaemum, depending on the species, the companion spikelet may be reduced or developed but always present. Thelepogon retains only the pedicel of the companion spikelet (Figs. 5a & b). Other characters which are more easily observed may become apparent as this species is studied more, e.g. specimens of Sehima nervosum have only one raceme per flowering culm and tend to have longer leaves (5-40 cm) than those seen on Thelepogon (5-12 cm).

Figure 3. Portion of a raceme of Thelepogon australiensis made up of two segments or internodes, showing exserted awn of the sessile spikelets. (CC-BY Queensland Herbarium, illustrator Will Smith) Figure 4a. Lower glume of sessile spikelets of Thelepogon australiensis showing scabrid keels or edges. (CC-BY Queensland Herbarium, illustrator Will Smith) Figure 4b. Lower glume edges of Thelepogon australiensis (MBA7155) showing scabrid edges.

Figure 5a. Illustration of raceme segment of Thelepogon australiensis showing naked pedicel and internode from two sides of spikelet cluster. (CC-BY Queensland Herbarium, illustrator Will Smith) Figure 5b. Naked pedicel adjacent sessile spikelet of Thelepogon australiensis (MBA7155)

Figure 6a. Inflorescence of Sehima nervosum (MBA7182 Figure 6b. Pedicelled spikelet and sessile spikelet of Sehima nervosum showing pedicelled spikelet and sessile spikelet (MBA7182)

Natural Values
Listed as Vulnerable in Queensland due to its very restricted distribution and small known population size (Nature Conservation Wildlife Regulation 2006).
Habitat
Currently only known from one locality north of the Archer River between Coen and Weipa (Fig. 7), where it is found in Piliostigma malabaricum low open woodland on cracking clay (Simon 1993).

Land Management Notes
As a vulnerable species Thelepogon will be subject to conditions of the Nature Conservation Act (1992).

Figure 7. Map of Cape York Peninsula bioregion

Figure 7. Map of Cape York Peninsula bioregion showing actual herbarium
collections (from BRI and CNS) (solid circle) and site records (open circle)
of Thelepogon australiensis. The green shading indicates areas where this
species might also be found, based on similarity of habitat to locations
where the species has been recorded. (Mapping supplied by P. Bannink,
DES). Data attribution: Environment and Science, Queensland
Government, Biodiversity status of pre-clearing and 2015 remnant regional
ecosystems series - version 10.0 licensed under Creative Commons
Attribution.

Resources:
AVH (2017) Australia’s Virtual Herbarium, Council of Heads of Australasian Herbaria, <http://avh.chah.org.au>, accessed 30 May 2017.
Nature Conservation (Wildlife) Regulation 2006. Online, accessed from https://www.ehp.qld.gov.au/wildlife/threatened-species/vulnerable/vulner.... Retrieved 28 April 2017.
Simon, B.K. (1993) Studies in Australian grasses, 8. A new species of Thelepogon. (Andropogonae: Ishaeminae) for Australia. Austrobaileya 4(1): 105-108.
Simon, B.K. & Alfonso, Y. (2011) AusGrass2, http://ausgrass2.myspecies.info/accessed on [20 March 2017].

Species Habitat

Currently only known from one locality north of the Archer River between Coen and Weipa (Fig. 7), where it is found in Piliostigma malabaricum low open woodland on cracking clay (Simon 1993).

Species Appearance

A tufted erect annual grass up to 140 cm tall (Fig. 1). Currently only known from one locality north of the Archer River between Coen and Weipa, listed as Vulnerable in Queensland and protected under the Nature Conservation Act (1992). Plants are recorded as having red stems particularly towards the base (Simon 1993). The leaves arise along the erect stems and are hairy along the sheath (that part which clasps the stem) and blade margins. Leaf blades are quite broad, 5-12 cm long and 6-10 mm wide. Spikelets (the basic flowering unit) are arranged in spikes or racemes (Fig. 2), with 1-3 spikes terminating a stem. The spikelets have a conspicuous exserted awn (bristle), the awn is up to 16 mm long and originates from a floret (a modified flower) within the spikelet. The awn is sharply bent just above its exsertion from the spikelet and twisted (Fig. 3). The lower glume of the spikelets are hardened and textured with small warty outgrowths (Figs. 4a & b).

Species Care

As a vulnerable species Thelepogon will be subject to conditions of the Nature Conservation Act (1992).