Allocasuarina duncanii

Allocasuarina duncanii, commonly known as Duncan's sheoak, or conical sheoak, is a species of flowering plant in the family Casuarinaceae and is endemic to Tasmania. It is a small dioecious tree that has branchlets up to 200 mm long, the leaves reduced to scales in whorls of seven to nine, and the fruiting cones 15–60 mm long containing winged seeds (samaras) 6–10 mm long.

Description
Allocasuarina duncanii is a small, erect, dioecious tree that typically grows to a height of up to 8 m. Its branchlets are up to 200 mm long, the leaves reduced to scale-like teeth 0.8–1.5 mm long, arranged in whorls of seven to nine around the branchlets. The sections of branchlet between the leaf whorls (the "articles") are 4–17 mm long and 0.9–1.4 mm wide. Male flowers are arranged in head-like spikes 7.5–13 mm long, with six to eight whorls per centimetre (per 0.39 in.), the anthers about 1 mm long. Female cones are cylindrical, on a peduncle 4–10 mm long. Mature cones are 15–60 mm long and 12–25 mm in diameter, the samaras dark brown to black and 6–10 mm long.

This sheoak is similar to A. monilifera that is mostly monoecious, and lacks the "conifer-like" habit of A duncanii.

Taxonomy
Allocasuarina duncanii was first formally described in 1994 by Lawrie Johnson and Dennis Morris in the journal Telopea from specimens collected near the headwaters of the Nicholls Rivulet in 1993. The specific epithet, (duncanii) honours "Mr Fred Duncan", who brought the species to the attention of botanists.

Distribution and habitat
Duncan's sheoak grows in shallow soil over dolerite, usually at altitudes above 500 m, on Mount Dromedary, the Wellington Range, Snug Tiers and on South Bruny Island.

Conservation status
Allocasuarina duncanii is listed as "rare" under the Tasmanian Government Threatened Species Protection Act 1995. The main threats to the species are inappropriate fire regimes, drought and climate change.