Selective breeding can produce heat-tolerant corals: new study

A close-up showing the detail of a Platygyra coral (credit Emily Howells)

Coral populations have the genetic potential to adapt to warming oceans, according to new research from researchers at Southern Cross University.

“Our previous work revealed that corals in an extreme environment have an exceptionally high heat tolerance, in part due to the genetic adaptation of the coral animal,” said Dr Emily Howells, senior researcher at the National Marine Science Center at Southern Cross University.

“In this study, we wanted to test whether we could transfer these beneficial genetic variants to a population of relatively heat-sensitive corals living in milder ocean conditions. “

The study led by Dr Howells and also involving Professor David Abrego of Southern Cross University was an international collaboration between New York University Abu Dhabi, Oregon State University, University of Science and King Abdullah Technologies, Zayed University, CSIRO, and Wollongong University.

The researchers crossed corals from the thermally extreme Persian Gulf with those of the same species from the milder Indian Ocean and measured the performance of many families of their offspring.

The team found that heat tolerance increased by up to 84% when Indian Ocean mothers were mated with Persian Gulf sires and was, on average, equivalent to offspring’s heat tolerance with both parents from the Persian Gulf.

A coral community with fish

A coral community in the Persian Gulf (credit Emily Howells).

“This was an impressive result, because while we expected to see an improvement in heat tolerance, the signal was much stronger than expected from the genetic contribution of single fathers, as the maternal effects also contribute to the tolerance of the offspring, “said Dr Howells.

Genome-wide sequencing of coral families confirmed these results by revealing that genetic variants positively associated with heat survival were primarily inherited from relatives in the Persian Gulf.

The researchers also deployed the offspring to the Indian Ocean site and found that the corals crossed with the Persian Gulf fathers survived as well as the purebred corals from the Indian Ocean, but both had longer survival. higher than the non-native Persian Gulf race corals.

These results demonstrate that corals can be selectively bred for better heat tolerance using corals from populations living in extreme or warmer environments that have a higher proportion of heat-tolerant genetic variants due to local adaptation.

“Selective breeding has the potential to be used to improve the resilience of targeted coral populations to global warming, but requires further testing before it can be implemented in response and restoration programs,” said the Dr Howells.

“However, the most important actions to improve the resilience of all coral populations are those that limit the extent of climate change.”

An unexpected finding from the study was that genetic variation was not limited to the Persian Gulf and was also present at low levels in the cooler populations of the Indian Ocean.

“One of the most exciting results of the study was that a small number of Indian Ocean sires produced offspring with surprisingly high heat tolerance, and these sires had some of the same genetic variants associated with the heat tolerance that prevailed in the Persian Gulf, ”said Dr. Howells.

“Such permanent genetic variation is essential for natural selection to occur in warming environments. “

Close-up of coral larvae

Platygyra larvae under a microscope (credit Emily Howells).

Co-author Dr David Abrego said ongoing international collaborations are critical to this work.

“This study has fostered more international collaborations as we investigate whether these heat-tolerant variants occur in other regions of the Indo-Pacific,” said Dr Abrego.

Dr Emily Howells’ current research is investigating permanent genetic variation for heat tolerance in Australian coral populations with support from the Hermon Slade Foundation and under the Reef Restoration and Adaptation Program, a partnership with the Australian government to help the Great Barrier Reef to resist, adapt and recover from the impacts of climate change.

“Our study, along with other recent research, indicates that some coral populations exhibit greater genetic variation for heat tolerance than previously thought,” said Dr Howells.

“Now, on the Great Barrier Reef, we are undertaking extensive assessments of the physiological and genetic variation that exists within and among breeding populations as well as between them. The objectives of this research are to develop diagnostic markers of heat tolerance in corals and to improve our understanding of the potential for adaptation to climate change.

Funding

This study was supported by National Geographic Society grant 9433-14 awarded to Emily Howells; and the Tamkeen CG007 grant awarded to John Burt.

Study details

EJ Howells, D. Abrego, YJ Liew, JA Burt, E. Meyer, M. Aranda, “Improving the heat tolerance of reef-building corals to future warming”. Science Advances 7, eabg6070 (2021).

DOI: 10.1126 / sciadv.abg6070

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