Drautabua (Acmopyle sahniana)

Drautabua (Acmopyle sahniana)

Drautabua (Acmopyle sahniana) is a gymnosperm belonging to the family Podocarpaceae, and a member of the wider and better known Pine family.

Also known as:

Local Names: Drautabua

Description

They have a straight tree trunk, up to 14 cm in diameter, and can grow to 8-12 m in height in the forest. In disturbed sites, they only grow up to 4 m in height. Drautabua, the only name recorded for the tree originates from the shape of its leaflets which are like that of a tooth of a whale (tabua) (Tuiwawa 1999).

Drautabua trees have few branches and most of which are at the top half of the tree.

The leaves are dark green and have a waxy appearance on the upper surface, and a dry, whitish appearance on the bottom surface. The leaves form two rows on the stem, which rises from the tree trunk. The leaves can only grow up to 1.7-24.0 mm in length, unlike the longer needle-shaped leaves of pine trees.

The young leaves are reddish purple in colour.

The reproductive structure of the Acmopyle, like other members of its family, is a cone-shaped pollen cone. The female cones are fleshy.

The seeds have green coloured fleshy receptacles when mature.

Distribution

Currently known from Viti Levu, in forests within the provinces of Namosi and Naitasiri, formerly recorded from Koroyanitu Range, Ba province but apparently lost from there now.

 Drautabua

Drautabua

 Drautabua (Acmopyle sahniana)

Drautabua (Acmopyle sahniana)

Habitat Ecology and Behaviour

The Drautabua has a very specific habitat – it has only ever been found in the rainforest of Viti Levu, in high elevations, at the top of very steep, narrow ridges approximately only 1m wide. Recorded populations have been found at sites located just below the elevation required for Montane Cloud Forests in Fiji. These parts of the forest are usually enveloped by cloud, and exposed to strong winds. The Drautabua is able to survive on soils of low fertility, even on just a small cliffside patch of soil, but are unable to do so at lower elevations. The tree can mature at around 5-10 years, at a height of 1m. At this age and height, the plant may be able to reproduce if the conditions are favourable. The reproductive cycle of Drautabua is unknown. Studies on this species have revealed that it is a unique Podocarp in that it is monoecious, meaning that both male and female cones come from the same individual. In contrast, many members of the same family are dioecious – male and female cones come form separate trees.

However, it has been observed that the two sexes do not occur on the same plant at the same time. They alternate between reproductive seasons. Until the reproductive behaviour of this plant is more intensively studied, we can only assume that it reproduces like other members of the Podocarpaceae whereby the pollen is transferred from the male cones to females via the wind. This mechanism of wind pollination probably accounts for the preference of this species to grow on the breezy ridge-tops of Viti Levu. While the pollination process has never been observed, the fact that the seeds have a fleshy green receptacle suggests that native frugivorous birds and bats feed on the fruit, thus aiding in the dispersal of this plant to other ridges and other parts of Viti Levu.

Threats

Drautabua may occur in other little researched montane forest areas in Fiji, but its current distribution of just three widely dispersed populations provides little assurance of its future survival. It is not known if formerly it had a wider distribution of populations on Viti Levu but the apparent loss of the Mt. Koroyanitu population which was recorded in 1947 but could not be located in a survey in 1997 is indicative of a long term decline. If a long-term decline is involved, Acmopyle sahniana may be extremely vulnerable to climate change induced changes to the upland microhabitat to which it is currently confined.

Conservation Status

The Drautabua is critically endangered because of its small, declining population. Preliminary efforts have been made to search for other populations and to conserve the known populations, as well as try to grow seedlings at lower elevations. No significant success was achieved. For this reason, specific locations of the remaining populations were not revealed. In 2003, just when it seemed that the world’s only viable populations were in the Korobasabasaga range and threatened by the Namosi copper mine development, another three reproducing populations were discovered in the Wabu Forest Reserve during a biodiversity study of the area by the members of the South Pacific Regional Herbarium of the Institute of Applied Sciences of the University of the South Pacific and other environmental non-governmental organisations (NGOs). These surveys initiated considerable conservation interest and it is this interest amongst local biologists, NGOs, landowners and government agencies which may result in the eventual conservation action to protect this little known species.

Remarks and Cultural Significance

The Drautabua is critically endangered because of its small, declining population. Preliminary efforts have been made to search for other populations and to conserve the known populations, as well as try to grow seedlings at lower elevations. No significant success was achieved. For this reason, specific locations of the remaining populations were not revealed. In 2003, just when it seemed that the world’s only viable populations were in the Korobasabasaga range and threatened by the Namosi copper mine development, another three reproducing populations were discovered in the Wabu Forest Reserve during a biodiversity study of the area by the members of the South Pacific Regional Herbarium of the Institute of Applied Sciences of the University of the South Pacific and other environmental non-governmental organisations (NGOs). These surveys initiated considerable conservation interest and it is this interest amongst local biologists, NGOs, landowners and government agencies which may result in the eventual conservation action to protect this little known species.

References

  • Bush (1997);
  • Tuiwawa (1999);
  • Tuiwawa and Naikatini (2003)