For the first time, scientists at The University of Texas at Austin have observed separate populations of corals diverging in their capacity to regulate their genes when adapting to the local environment.
The research, published in Nature Ecology and Evolution, reveals a new way for coral populations to adapt that may help predict how they will fare in the face of climate change.
The findings was based on populations of mustard hill coral (Porites astreoides) living around the Lower Florida Keys. Corals located close to shore are adapted to a more variable environment due to the greater fluctuation in temperature and water quality in the vicinity, developing the ability to adapt to occasional stressful events that offshore corals are spared.
During the experiment, researchers swapped 15 genetically distinct coral colonies from a close-to-shore area with 15 colonies of the same species from offshore waters. After a year, the two populations showed differences: Formerly inshore corals transplanted offshore changed their gene activity dramatically to closely resemble the locals, whereas offshore corals transplanted inshore were able to go only halfway toward the local gene activity levels. In short, corals that originated from the more variable, close-to-shore environment were more flexible in their gene regulation, enabling them to adapt better to their new environment.
“It is exciting that populations so close together – these reefs are less than five miles apart – can be so different,” said corresponding author Carly Kenkel, currently affiliated with the Australian Institute of Marine Science.
“We've discovered another way that corals can enhance their temperature tolerance, which may be important in determining their response to climate change,” she added.
Gene regulation – the body's ability to make specific genes more or less active – can be inherited and are pivotal for adapting to environmental change. It was already known that separate populations often develop differences in average levels of gene activity, but scientists have now found that populations can also diverge in their ability to switch genes on and off.
“We show that one population has adapted to its more variable environment by developing an enhanced ability to regulate gene activity,” said co-author Mikhail Matz, an associate professor in the Department of Integrative Biology.
The lack of flexibility took its toll on the offshore corals, which did not fare well at the inshore reef and experienced stress-induced bleaching. Their higher bleaching levels were linked to the diminished ability to dynamically regulate activity of stress-related genes, confirming that flexibility of gene regulation was an important component of adaptation to the new environment.
“We saw different capacity for gene expression plasticity between coral populations because we looked at the behaviour of all genes taken together instead of focusing on individual genes,” said Kenkel. “If we hadn't, we would have missed the reef for the coral, so to speak.”