Hope for coral reefs

2003-04-29 11:29

Sydney - New research showing that key species of coral can cross-breed has fuelled hope that coral reefs will be able to cope with climatic and environmental change, an Australian scientist said on Tuesday.

Madeleine van Oppen of the Australian Institute of Marine Science said her study of the Great Barrier Reef off northeastern Australia found evidence of cross-breeding in the major Acropora genus of coral species.

Her discovery challenges the long-held belief that cross-breeding, or hybridisation, is only significant in the evolution of plants and not animals.

Van Oppen said the new information indicates that coral species can develop a greater diversity of DNA that in turn should help them adapt to environmental changes that are threatening reefs worldwide.

Acropora is considered one of the most important corals in the Pacific and Indian Oceans and the Caribbean Sea because it is one of the most plentiful, at 180 species rich. "We believe hybridisation has contributed to the enormous success of Acropora," Van Oppen said in a statement.

Evolutionary advantage

"The high level of genetic diversity provides an evolutionary advantage to this group of corals because the more genetic diversity there is within a population or species the more likely it is to be able to respond to environmental changes," she said.

Van Oppen, a geneticist, said it was too early to say if this diversity was enough to permit coral to survive one of its greatest threats -bleaching caused by rising sea temperatures - but she said the cross-breeding "does create an enormous capacity for adaptive evolution".

"The next step for us is to go and experiment to show that they would be able to adapt to environmental change," she said. Van Oppen and her team have spent six years studying mass coral spawning on the Great Barrier Reef, the biggest reproductive event in the animal kingdom.

From a base camp on Magnetic Island in the reef, Van Oppen and her team have been collecting coral eggs and sperm for cross-fertilisation experiments. "They don't cross-breed all the time, every spawning, but they do so occasionally and that's enough to keep this genetic diversity high," she said.

"Because they throw all their sperm and egg at the same time, they can actually cross-breed." Van Oppen said it was not clear whether the newly discovered evolutionary patterns were restricted to Acropora or could be generalised to other groups.

"We have found one other coral genus, Montipora, also shows patterns of evolution similar to those in Acropora, suggesting that hybridisation occurs in this coral genus as well," she said.

The Great Barrier Reef, covering more than 345 000 square kilometres, is considered the world's largest living organism and is one of Australia's main tourist attractions. - Sapa-AFP

- SAPA