Corals mate with other species to survive

October 22nd, 2008 - 12:53 pm ICT by IANS  

Sydney, Oct 22 (IANS) Faced with a dire shortage of mates of their own kind, corals may be able to cross-breed with certain other coral species to avoid extinction, suggests a new study. This finding, released by scientists at the Australian Research Council (ARC) Centre of Excellence for Coral Reef Studies, has raised hopes for the ability of the world’s corals to withstand the rigours of changing climates and human impacts, said study co-author Zoe Richards.

“It is often assumed that rare coral species face higher risks of extinction than common species because they have very small effective population sizes, which implies that they may have limited genetic diversity and high levels of inbreeding and therefore be unable to adapt to changing conditions,” Zoe said.

“When we studied some particularly rare species of Acropora (staghorn corals), which you might expect to be highly vulnerable to extinction, we found some of them were actually hybrids - in other words they had cross-bred with other Acropora species.”

“This breaks all the traditional rules about what a species is. By hybridising with other species, these rare corals draw on genetic variation in other species, increasing their own potential to adapt to changing conditions.

“At this stage how it came about and who the breeding partners are isn’t entirely clear, but what is evident is that rare corals previously thought vulnerable to extinction may have more ability to adapt than initially expected,” she explained.

Acropora are the main reef-builders throughout the Indian and Pacific Oceans, and so of critical importance to the ability of reefs to cope with changing conditions. However, till now, very few examples of hybridisiation were known, and some people did not even accept that corals can cross-breed, Zoe says.

“When we looked at the genetic history of rare corals, we found that they exhibited unexpected patterns of genetic diversity. This suggests that, rather than being the dying remnants of once-common species, they may actually be coral pioneers pushing into new environments,” says an ARC press release.

“This is good news, to the extent that it suggests that corals may have evolved genetic strategies for survival in unusual niches - and may prove tougher to exterminate than many people feared. With such tricks up their sleeve, it is even possible that the rare corals of today could become the common corals of the future.”

Co-author David Miller of James Cook University said the discovery is a refreshing piece of good news amid the frequently gloomy reportage about corals nowadays.

“Hybridising with another species actually makes a lot of genetic sense if you are rare and the next colony of your species may be hundreds of kilometres away. It suggests these creatures are far more resilient than we thought, based on what we know from the behaviour of land animals.”

These findings were published in the September issue of PloS One.

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