In a ground-breaking collaboration, scientists from Queensland Museum and James Cook University have described the first new species of staghorn coral from the Great Barrier Reef since the 1980s. This discovery has shattered previous assumptions and exposed a hidden world of coral diversity.
Working alongside national and international colleagues from the United States National Museum of Natural History – Smithsonian Institute, two new species of staghorn coral have been described. One found in Fiji, the Cook Islands, Japan, and elsewhere across the Indo-Pacific and the other from the Cook Islands in the South Pacific.
Traditionally, coral identification relied on shape, however this method proved problematic due to the influence of environmental factors on coral appearance. By examining and comparing coral genomes (DNA), the team has gained unprecedented insights into the true extent of coral diversity.
Queensland Museum Senior Scientist and Curator of Corals and Senior Lecturer from James Cook University Dr Tom Bridge said the research shows that the true diversity of corals had been overlooked.
“We looked at a group of corals in the genus Acropora, commonly called staghorn corals, which are the most diverse and abundant corals on the reef. When you look at their shape many species look quite similar, but when we looked at the corals DNA we found that there were far more species than we thought - what was previously considered a single-species occurring across the Indo-Pacific was actually several species, each with a much smaller range,” Dr Bridge said.
“Some of these species have been named previously but were not considered distinct species because they look similar to other species in other parts of the world. So we have ‘resurrected’ those old names so people recognise that they are unique and distinct species.
“One of these species, Acropora tenuis, was thought to occur all across the Indo-Pacific, from Tahiti in the east all the way to Africa and as far north as the Red Sea and Japan.
“What our research showed is that the species is only found in a relatively small region of the South Pacific, and what we were calling tenuis on the Great Barrier Reef is a distinct species found in eastern Australia and Papua New Guinea. Similar looking corals from Western Australia, Japan and the western Indian Ocean are also completely different species.
“We also found species that were completely undescribed. One of these was from the Great Barrier Reef, one of the best studied reefs in the world, which highlights why we need to continue to research and discover how much more there is to understand about coral diversity.”
The other new species is the first described from the Cook Islands in the South Pacific. Dr Teina Rongo from Kōrero o te 'Ōrau, environmental NGO based on the island of Rarotonga, said the study highlights that these remote islands support unique and distinct biodiversity that warrants further exploration and conservation efforts.
“We recognise that this study only examined one island in the Cook Islands, and there remains a large part yet to be explored. This study certainly provides an opportunity to do more in this region, especially with regards to endemism and conservation value,” Dr Teina Rongo said.
Identifying the species using DNA was only part of the challenge. To resolve the identities of the two new species, the research group had to scour the history books to determine if previous descriptions existed.
Professor Andrew Baird from James Cook University said that identifying and describing the new species required a lot of detective work, examining old specimens in museums collected almost two centuries ago.
“A lot of the time these distinct species were described decades or centuries earlier, but the names have fallen out of use,” Prof. Baird said.
“This is exactly the case here – the Great Barrier Reef ‘tenuis’ was actually described by a scientist working in the Natural History Museum in London in 1892, based on a specimen collected from Thursday Island by the British naturalist William Saville-Kent, who travelled extensively on the Great Barrier Reef in the early 1890s. The species was named kenti after him, and so what we have done is ‘resurrect’ that name.”
Dr Andrea Quattrini from the Smithsonian Institution National Museum of Natural History said the findings of this paper were important as A. tenuis is among the most-widely studied corals.
“What we have found is that scientists in different parts of the world are actually studying different species – even though they think it is the one species,” Dr Quattrini said.
“For example, three different studies have published Acropora genomes from different parts of the world, but our study shows that none of them are currently assigned correct species identities. Two are identified as A. tenuis, but in fact neither are A. tenuis.
“These results also have implications for understanding extinction risk in corals. While coral bleaching has resulted in declines in coral abundance, we have little idea how this has affected the populations of different species.
“Currently, most staghorn coral species are considered to have large geographic ranges spanning most of the Indo-Pacific, making them less vulnerable to extinction.
“However, smaller ranges mean many species may be more vulnerable to extinction than we previously thought. Even worse, there is a risk these species may go extinct before we even realise, they exist.”
The work is part of Queensland Museum’s Coral Bank project, which seeks to create a curated genomic and taxonomic repository of Australia’s threatened coral reefs.
Coral Bank will help inform our understanding and conservation efforts of the Great Barrier Reef.
Queensland Museum CEO Dr Jim Thompson said the research being undertaken by Queensland Museum scientists as part of Coral Bank was revolutionising our understanding of the diversity and biogeography of corals.
“Coral Bank provides an opportunity to establish the first comprehensive collection of corals in northern Australia,” Dr Thompson said.
“This remarkable collection includes high-resolution photographs of living corals in the field, skeletal specimens that are housed in the museum and tissue samples for DNA analysis.
“I congratulate Dr Bridge and his team for their transformative work in taxonomy and describing two new species of coral.”
The new paper was published in Zoological Journal of the Linnaean Society.