Declining Corals May Drastically Affect Crustacean Biodiversity

Brett Smith for – Your Universe Online
With many scientists expecting climate change to have a devastating effect on the world’s coral reefs over the coming century, new research from the University of Florida indicates that crustacean populations living near rapidly declining reef habitats could be at risk.
Appearing in the November issue of the journal Geology, the new study is based on an analysis of the fossil record surrounding decapod crustaceans, a group that includes shrimp, crab and lobster.
“We estimate that earth’s decapod crustacean species biodiversity plummeted by more than 50 percent during a sharp decline of reefs nearly 150 million years ago, which was marked by the extinction of 80 percent of crabs,” explained study author Adiël Klompmaker, a postdoctoral researcher at the Florida Museum of Natural History on the UF campus.
“If reefs continue to decline at the current rate during this century, then a few thousand species of decapods are in real danger. They may adapt to a new environment without reefs, migrate to entirely new environments or, more likely, go extinct.”
According to study researchers, their paper is the first comprehensive look at the rise of decapod crustaceans in the fossil record. The study is based on a worldwide specimen database of fossils from the Mesozoic Era, which spanned from just over 250 to 66 million years ago.
The researchers tracked patterns of diversity and found that an ancient increase in the number of decapod species was related to the abundance of reefs, due to the reefs serving as a place both to find shelter and forage. Dubbed the “Mesozoic decapod revolution,” this period in Earth’s history saw a 300-fold increase in species diversity over the previous period and in the rapid evolution of crabs.
The researchers noted the difficulty in compiling the data for the study since most decapods possess a fragile exoskeleton that does not fossilize well.
“Only a scant fraction of decapod crustaceans is preserved in rocks, so their fossil record is limited,” said study co-author Michal Kowalewski, curator of invertebrate paleontology at the Florida Museum. “But, thanks to efforts of paleontologists many of those rare fossils have been documented all around the world, finally giving us a chance to look at their evolutionary history in a more rigorous, quantitative way.”
“This new work builds a good case for the role of reefs in promoting the evolutionary diversification of crustaceans,” added David Jablonski, a paleontologist in the department of geophysical sciences at the University of Chicago who was not directly involved in the study.
“We have to take their argument for the flip side of that story very seriously. The positive relation between reefs and crustaceans implies that the damage caused to reefs by human activities — from overfishing to ocean acidification — is likely to have cascading consequences for associated groups, including crustaceans.”
He pointed out that the new study also opens up several avenues for future research.
“It would be very interesting to extend this analysis into the Cenozoic Era, the 65 million years leading up to the present day,” Jablonski said. “And it would be valuable to look at the spatial structure of the crustacean diversification, for example how closely their diversification was tied to the extensive reefs in the western Pacific and was damped in the eastern Pacific with their much sparser contingent of reefs.”

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