Smith, I. R., K. Withers, and J. Billingsley. 2007. Maintaining the Ancient Bunya Tree (Araucaria bidwillii Hook.) - Dispersal and Mast Years. Presentation given at the 5th Southern Connection Conference, Adelaide, South Australia, 21-25th January 2007.

Abstract

The bunya pine (Araucaria bidwillii) is the last surviving species of the Section Bunya of the genus Araucaria. This section was diverse and widespread during the Mesozoic with some species having cone morphology similar to A. bidwillii, which appeared during the Jurassic. A. bidwillii is a sacred tree for the Aboriginal people and it has also been recognized as an important tree, planted throughout the world.

A. bidwillii now has only limited distribution within Australia. There appear to be two possible explanations. One is climate change and a drying out of Australia with loss of rainforest habitat. The second is that the species has poorly dispersed seed. The cones are large, soft-shelled and nutritious and fall intact to the ground beneath the tree before dehiscing. In the past, larger animals such as dinosaurs and large mammals may have dispersed A. bidwillii. These possible ancient vectors are clearly absent now.

There are no documented dispersal agents for the seeds of A. bidwillii, although there are anecdotal reports of some native fauna as possible carriers or predators of the seeds and tubers. This study examined whether seeds were destroyed or dispersed by native fauna in natural stands and if there were variations in mast years for A. bidwillii.

In 2003, during a mast year for A. bidwillii, tagged seeds were placed and monitored at two sites in southeast Queensland. Some seeds were eaten and some germinated in situ. However, some were removed and carried 8m outside the parent tree canopy and uphill from parent trees, possibly allowing ridge-top germination.

In 2006, seed were placed in forest areas and were monitored with a CCD camera capable of recording scenes illuminated by infra-red light and the type of species eating or dispersing the seed were indentified. It was a poor year, but seeds were carried and eaten by the short-eared possum (Trichosurus caninus). The fawn-footed melomys (Melomys cervinipes) ate the seed in situ, but did not disperse the seed.

The short-eared possum (Trichosurus caninus) is able to disperse the seed of A. bidwillii which may help maintain this ancient tree.