Mixing things up: Acropora rongelapensis from Rongelap Atoll in the Marshall Islands.

Credit: Silvia Pinca

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SYDNEY: Rare species of corals are cross breeding with one another in a bid to prevent extinction, researchers have found.

The findings hint at a new way that threatened reefs may be able to adapt to changing environmental conditions, particularly climate change.

Marine biologists at James Cook University in Townsville, Queensland, discovered that when faced with low population levels, the eggs of some rare species of Acropora corals allow themselves to be fertilised by the sperm of other species, generating previously unknown hybrids.

More ability to adapt

"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" said Zoe Richards lead author behind a study detailing the find in the journal PloS One.

Acropora is the dominant reef building coral in the Indian and Pacific oceans. It is predominantly found in reef flats, reef crest and upper reef slope habitats with some rare species occurring outside of these habitats.

For the study, Richards' team collected samples of tissue and skeleton of 14 rare and eight common Indo-Pacific species of Acropora from the waters of the Great Barrier Reef, the Marshall Islands and Papua New Guinea. They then sequenced the DNA of those species and compared them to the sequences of three rare species of Acropora.

The study revealed that these three corals – Acropora pichoni, Acropora kimbeensis and Acropora papillare – are likely to be hybrids created by cross-fertilisation by the other species, rather than individual species in their own right.

Special tricks

According to Richards, there were previously few known examples of Acropora hybrids. She believes that the hybrid individuals may be found outlying the main reefs, in niche habitats, where their unusual combination of traits gives them a competitive advantage.

"This is good news, to the extent that it suggests that corals may have evolved genetic strategies for survival in unusual niches," she said of the find. "With such tricks up their sleeve, it is even possible that the rare corals of today could become the common corals of the future."

John Pandolfi, an expert in the long-term ecology of coral reefs at the University of Queensland in Brisbane said that the study is very exciting because it highlights the significance of hybridisation in reef corals. He added that studies like this can help researchers to "understand the origin of modern biodiversity and the maintenance of modern ecosystems" including how these ecosystems came to be and how they are changing.