Why Are Large Fruits Rare In Australian Rainforests?

Australia's lush rainforest is unlike other forests in Africa, South America, and the South Pacific, according to a study published in the Proceedings of the Royal Society. What sets Australian forest apart is its relative lack of large-fruit bearing plants, which makes this already stressed ecosystem comparatively vulnerable to disruption.


The Royal Society paper examined plants with fleshy fruit and the animals that disperse their seeds to get a picture of the symbiotic relationship such plants form with fruit eaters in the forest.

The study found that Australia's small-fruited plant species were not only more diverse than the large-fruits, the smaller species were at a competitive advantage in areas where deforestation has occurred. One likely mechanism for this ecological imbalance is the speed with which small-fruited plants move in to occupy open ground where the large-fruited plants have been cut down or burned.


This shift in Australia's native flora is a serious problem for the entire rainforest. Fruit-bearing plants such as Australia's native “black apple” depend on large animals to eat them in order to successfully disperse. The seeds are usually either carried a short distance from the parent tree or over a much longer distance in the animals' guts. The seeds of some species may be carried by different types of animals, but the larger fruits in particular need specific animals to disperse them.

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At issue for Australian forests is the question of human intervention. In order to be healthy, rainforests must have a natural distribution of different species of plants. With the general decline of Australia's native animal stock of herbivores, specifically the fruit-eaters of the eastern forests, it may become necessary for conservation authorities to take on the responsibility of planting the seedlings of at-risk species in cleared and recovering land.


Losing an entire type of plant weakens already-troubled Australian woodland, and the lack of such plants can conceivably discourage the threatened populations of large herbivores from moving into recovering forest lands. Australia's rainforests are not the only rainforests in danger, and you can help. Find out how you can save an acre of rainforest for Sumatran wildlife.

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