"If everything spawns at the same time there’s a good chance egg and sperm will meet,’ said Dr Madeleine van Oppen, who is a geneticist studying whether sperm and egg from different coral species cross-fertilise.

Dr van Oppen came to north Queensland from the UK and, before that, the Netherlands in 1997 to research coral hybridisation. She is a leading marine genetics researcher at the Australian Institute of Marine Science and is a pioneer in this field of research.

When scientists discovered coral spawning 15 years ago it unlocked the key to the proliferation of the reef but Dr van Oppen’s research into hybridisation sheds light on the evolution of the reef’s biodiversity and now its evolution into the future.

The hybridisation project has been a collaborative effort between AIMS and James Cook University biology Associate Professor Bette Willis from the school of Marine Biology and Aquaculture, and Dr David Miller, a Reader in the Comparative Genomics Centre. They make a formidable team with extremely impressive credentials.

After six years of experimentation, scientists believe they have made a major step towards understanding how hybridisation has helped shape modern day reefs.

Dr van Oppen and her colleagues have found that cross-breeding between Acropora corals occurs occasionally on the reef, not just in a test tube.

"We know it happens in nature because pieces of DNA from one species can be found in others. We have found an exchange of genes between species."

It is not known why or when it happens, or whether there are environmental influences at play. Dr van Oppen stresses that: "It happens too infrequently to cause species to merge and lose their genetic distinctiveness. It yields high levels of genetic diversity. This 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 able to respond to environmental changes."

"I’m not saying it can survive rising sea temperatures, it is too early to say. However, these high levels of genetic diversity in acroporid corals does create an enormous capacity for adaptive evolution," she said.

Variety of Acropora corals in the field. Photo: Colin Munn

Dr van Oppen checking corals for the presence of mature eggs. Photo: Colin Munn

The research challenges the long-held belief that hybridisation is significant for the evolution of mainly plants and not animals. Dr van Oppen said it has been difficult convincing the scientific community that corals do have the ability to cross-fertilise in nature.

The fieldwork has focussed on the Acropora genera of corals, one of the most important corals in the Pacific and Indian Oceans, simply because it is very widespread, common, and the most species rich. There are at least 180 species involved.

"We believe hybridisation has contributed to the enormous success of the species," Dr van Oppen said.

"At this stage it is not clear whether these evolutionary patterns are restricted to Acropora or whether it can be generalised to other groups," said Dr van Oppen.

"We suspect hybridisation to be widespread, much more widespread than initially thought. Studies coming from overseas suggest other hard corals also hybridise. There’s evidence hybridisation between species has occurred in at least two other coral families," she said.

Transferring coral specimens from the sea into the collection pool. Photo: Neal Cantin

Coral colonies placed in collection pool waiting for spawning event. Photo: Neal Cantin