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The hidden diversity of coral species could help save them

Coral species that appear to be identical to each other are turning out to be genetically distinct. This hidden diversity could be much more important for conservation than what was previously realized, according to researchers at the California Academy of Sciences.

In collaboration with an international team of experts, the researchers are taking a new approach to studying hidden coral species by investigating their ecological differences, which have been largely overlooked. 

“We know we are greatly underestimating the true number of coral species because of this hidden diversity,” said study lead author Pim Bongaerts. 

“In our study, we provide one of the first clear examples of how coral species that look identical can be very different in terms of their ecology and physiology, from when they reproduce to what depths they prefer. This means that our current framework for classifying reef-building corals based primarily on morphology is limiting our ability to understand and protect them.”

The experts conducted one of the most extensive genomic studies of corals to date, including DNA samples from more than 1,400 individuals. The analysis showed that the serpent coral, one of the most widespread corals across the Indo-Pacific, is actually four different species that evolved millions of years ago. 

The researchers were stunned when they realized that the four species are indistinguishable from each other, even at a microscopic level. This prompted the team to look for ecological differences that may have been missed.

An investigation was launched using remotely-operated vehicles and specialized deep diving gear to analyze corals from shallow depths down to 80 meters beneath the surface. 

While individual corals from each species were spotted across the entire range, the experts discovered that each species had distinct depths where they were most abundant. In addition, there were differences in physiological traits, such as protein content, that affect each species’ ability to survive and thrive at their preferred depths.

“Knowing what corals thrive where and at which depths is crucial for reef conservation,” said study co-author Professor Ove Hoegh-Guldberg of the University of Queensland. 

“Most marine protected areas only protect shallow reefs, which means that hidden species at mesophotic depths are being overlooked by current conservation strategies. We need to give this gap in protection some further thought.”

“For years we have asked ourselves about the relevance of this hidden diversity, wondering if we are missing something important,” said study co-author Alejandra Hernández-Agreda. 

“By using all of the tools at our disposal to analyze not just the morphology, but all these other aspects of these species as well, we now show how this hidden diversity can mask major differences in these species that could translate to their ability to cope with the rapidly changing conditions of our world’s oceans.”

The researchers hope their findings reveal the importance of taking a holistic approach to understanding hidden coral species that are potentially harboring key differences which impact global conservation efforts.

“At a moment when reefs around the world are experiencing rapid degradation, it is critical to start capturing this hidden diversity – not only of species, but of how they live and function – to improve our understanding and ability to protect these fragile ecosystems,” said Bongaerts.

The study is published in the journal Current Biology.

By Chrissy Sexton, Staff Writer

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