Genomic data “captures corals in the process” of speciation and adaptation

Diversity in Hawaiian corals is likely driven by coevolution

A study funded by the National Science Foundation of the United States conducted by researchers from the University of Hawaii at Mānoa revealed that diversity in Hawaiian corals is likely driven by co-evolution between the coral’s host, its algal symbiont, and the microbial community. The results are published in Nature Scientific Reports.

As coral reef ecosystems have rapidly collapsed around the world in recent decades, there is widespread concern that corals may not be able to adapt to changing climatic conditions and much of the biodiversity in these ecosystems may be lost before they are studied and understood.

Coral reefs are among the most biodiverse ecosystems on earth, but it is unclear what causes them to speciate and diversify in the ocean, where there are few physical reefs that could separate populations.

The researchers used huge amounts of metagenomic sequencing data to try to understand the main factors of adaptation and variation in corals.

“Corals have incredible variation with such a wide range of shapes, sizes and colors that it’s really difficult even for scientists to spot different species,” said Zac Forsman, lead author of the study.

Forsman and colleagues looked at genetic relationships in the coral genus Porites, which forms the basis of many coral reefs around the world. Scientists identified coral genes, algal symbionts and bacteria that were most strongly associated with coral bleaching and other factors such as the shape (morphology) of the coral colony.

They found relatively few genes associated with bleaching, but many associated with distance from the coast and colony morphologies that dominate different habitats.

“Unexpectedly, we found evidence that these corals have adapted and diverged very recently in depth and distance from shore,” says Forsman. “Algal symbionts and microbes were also in the process of diverging, which implies that coevolution is involved. It is as if we had caught them in the act of adaptation and speciation “.

“As global environmental change intensifies, it is more important than ever to understand the ability of critical ecosystems to respond to that change,” adds Sam Scheiner, program director at NSF’s Division of Environmental Biology. “This study is a step in that direction.”