Coral reefs are evolution hotspot

Victoria Gill, BBC News 7 Jan 10;

Coral reefs give rise to many more new species than other tropical marine habitats, according to a new study.

Scientists used fossil records stretching back 540 million years to work out the evolution rate at reefs.

They report in the journal Science that new species originate 50% faster in coral reefs than in other habitats.

The team says its findings show that the loss of these evolution hotspots could mean "losing an opportunity to create new species" in the future.

Coral reefs harbour a huge number of marine species - they are often likened to rainforests in terms of their biodiversity.



But they also provide a "pump of new marine species", according to Wolfgang Kiessling the scientist from Humboldt University in Berlin, Germany, who led this study.

He and his colleagues examined the fossil record to find the earliest evidence of benthic creatures - animals that live on the seafloor.

These creatures provide a good record of evolution. They remain on the seafloor once they die, and are often fossilised along with some of the remains of their original habitats.

This team of scientists looked for the earliest fossils from each benthic genus, or group of species, in the fossil record.

"We checked when and where each genus first occurred, explained Dr Kiessling. "So for example, if the earliest fossils were 300 million years, we asked: 'Did it occur in a reef or outside'."

He and his colleagues had access to a record stretching back to the Cambrian explosion - when the vast majority of complex organisms are believed to have emerged more than 540 million years ago.

This huge data set was compiled by an international project called the Paleobiology Database, which was started in 2000.

"We had the best documentation of the fossil record at our fingertips," Dr Kiessling told BBC News. "And there was also the geological context there, so we knew where each species occurred.

"Our study shows that reefs are even more important than currently assumed. They are not only ecologically important for the marine environment, but also in an evolutionary sense."

But Dr Brian Rosen, a zoologist at the Natural History Museum in London, UK, warned that the accuracy of fossil records alone was "notoriously difficult to gauge from the literature".

He added that it could be useful for independent experts to re-examine some of the fossilised creatures.

Data "generated by direct examination of the specimens themselves by the relevant taxonomic specialists" is more reliable when it comes to working out important evolutionary patterns, he said.

Carl-Gustaf Lundin, head of the marine programme at the International Union for Conservation of Nature (IUCN) said that this was a "very welcome paper".

"Studies like this provide conclusive evidence that reefs are centres of marine biodiversity," he told BBC News. "And now we see their importance in the evolutionary history of the planet."

He added that currently the planet was losing 2% of its reefs each year, mainly because of increasing ocean temperature bleaching and stunting the coral's growth. And ocean acidification making it more difficult for corals to build their skeletons.

Dr Kiessling said: "If we lose reefs we lose [an] opportunity to create new species by evolutionary processes."

Coral reefs crucial to origin of new marine species, finds study
New research provides a new incentive to protect reefs, overturning ideas that coral sealife originated elsewhere
David Adam, guardian.co.uk 7 Jan 10;

Coral reefs give birth to a dazzling number of new species of sea creatures, according to a study that highlights their critical role in marine ecosystems.

Scientists have found that the reefs not only harbour amazing biodiversity, but are actively involved in the generation of new life forms. The study overturns conventional thinking that much of the sea life in coral reefs originated elsewhere.

Wolfgang Kiessling of the Humboldt University of Berlin, who led the study, said: "We found that coral reefs are very active at generating biodiversity in the oceans, and that they export biodiversity to other ecosystems. This was a surprise because many people had assumed that reefs were ecological attracters – that species go there from other places."

He and colleagues in Germany and the US studied a database of fossil organisms that lived on the sea floor from the Cambrian period, about 500m years ago. They compared the number of new genera that first appeared in coral reefs with those in other shallow-water environments and found the reefs were responsible for about 50% more. The results are published tomorrow in the journal Science.

The team looked at fossils of so-called benthic organisms, such as starfish, clams and corals that live on the seabed. They ignored fossils of fish, which do not offer clues to where they evolve, because after they die their remains can float elsewhere.

Kiessling said the study offered extra incentive to protect coral reefs. "If we lose the coral reefs we lose the ability for marine ecosystems to generate new species in the future. I suspect that new species evolve every single day, but unfortunately not as fast as they go extinct."

Increasing carbon dioxide in the atmosphere damages coral as seas become warmer, which causes the coral to bleach, and become more acidic, which makes it hard for the tiny animals to repair their exoskeletons.

Experts say the world has already passed the safe level of carbon dioxide in the atmosphere for coral reefs, and even the most ambitious carbon cuts planned for coming decades will fail to save them.

Another Reason to Save Coral? Reefs Are Responsible for Ocean Biodiversity
An analysis of the fossil record shows that coral reefs are most often responsible for the diversity of sea life
David Biello, Scientific American 7 Jan 10;

The Great Barrier Reef is the largest living structure on Earth. It might also represent the most prolific cradle for new types of animals on the planet, according to new research published in the January 8 edition of Science.

"In the oceans, new species and genera tend to originate in the tropics and in the shallows near shore," says paleobiologist Carl Simpson of Humboldt University in Berlin, one of the researchers on the new paper. By using a massive collection of data on fossils from mollusks to South American mammals, which records where a fossil was found, how often it is found and what accompanied it, Simpson and his colleagues find "that a majority of genera first evolve in reefs and then later expand to other habitats."

In fact, of the 6,615 seabed invertebrates surveyed in the so-called Paleobiology Database, 1,426 evolved in a reef ecosystem. And the result is not just an artifact of reef and shallow-water fossils being relatively more studied. "Reefs are actually rare compared to other habitats," Simpson notes. "If anything, there is a bias against finding that reefs are cradles."

The phemonenon of reefs acting as cradles of biodiversity seems to have peaked in the Paleozoic—from 542 million to 251 million years ago—for reasons that are unclear. One possibility is that by seeding other environments with new species, reefs undercut their own preeminence as cradles. "The consequence would be that reefs become one of many important cradles, rather than the most common cradle," Simpson says.

And reefs do not seem to have helped the oceans rebound from mass extinction events, like the one at the end of the Paleozoic era that wiped out as much as 90 percent of marine life. That's likely because "reef-building as a process had to recover from mass extinction events, because the ecosystem engineers that built reefs were severely affected," says marine scientist Richard Aronson of the Florida Institute of Technology, who was not involved with the study. "Reefs in general were not available to enhance biodiversity rebound because they first had to be reconstituted as viable ecosystems."

But coral reefs do offer a variety of ecological niches and "bumpiness," as Aronson puts it, or a "great variety of physical spaces, [water] flow regimes and other ecological opportunities." That has made them cradles not just for sponges and the like but also snails, shrimps, urchins, fishes and even extinct animals like trilobites.

Plus, vicious competition for space and food on a reef leads to a lot of "turnover," Simpson notes, or extinctions that allow for new species to develop as new habitats form or ecological niches open. "If turnover is high, then the brief window of opportunity for new species is a common occurrence."

According to some mathematical estimates, 99.9 percent of all species that have ever existed are now extinct. As it stands, estimates of the number of species on Earth at present range from five million to as many as 100 million, with science having identified only two million members of the biodiversity extant today. That means literally billions of species have come and gone in the 4.5 billion years Earth has existed.

New research will be needed to determine exactly why reefs are such efficient cradles for new life-forms. But the threats faced by coral today—from rising ocean acidity to agricultural runoff and rampant disease—do not bode well for marine biodiversity in the near future. After all, it is possible that during mass extinction events the destruction of reefs might have played a role in the decline of diversity in other marine environments, as well. As Aronson asks: "If modern reefs continue to degrade, will that have cascading evolutionary consequences for other ecosystems by cutting off the supply of new genera?"