A Helping Hand for Evolution?

Climate change is progressing so rapidly, and is having such pervasive effects on the environment, that many organisms won’t evolve fast enough to survive. Encouraging the prevalence of genes that confer resistance to, say, drier or hotter climes, takes both time and multiple generations of reproduction.

Humans, however, could turbocharge that process. People have already practiced this for ages using selective breeding—crossing organisms with desirable traits to enhance those effects in their offspring.

Under the moniker “assisted evolution,” this practice is now being employed to help corals adapt to the warmer, more acidic waters expected with climate change.

Hotter waters are causing corals in the tropics to bleach, or expel the symbiotic dinoflagellate microbes that infuse them with color. The dinoflagellates are photosynthetic and supply coral with a critical source of food.

Bleaching is thought to give corals the chance to pick up new microbes able to function under the new conditions. But many unable to find suitable new partners, and die instead.

In a bid to make their coral more resistant to bleaching, Ruth Gates of the Hawaii Institute of Marine Biology, and Madeleine van Oppen of the Australian Institute of Marine Sciences, are crossbreeding local corals that survive bleaching events in the lab to create heat-tolerant supercorals.

Cartoon by Rohan Chakravarty,
Cartoon by Rohan Chakravarty,
[space height=”10″] Stephen Palumbi of Stanford University and colleagues are now selecting corals to restore damaged reefs in American Samoa by putting them through stress tests in heated aquariums. The corals that survive with the most chlorophyll content are chosen for outplanting.

Assisted evolution requires a considerable amount of time—the months or years between generations—to begin to produce results. And in most species, identifying individuals with greater tolerance for climate change isn’t as easy as spotting unbleached coral. So while the idea of breeding individuals better able to make a go of it in the conditions of the future is appealing, assisted evolution for conservation purposes hasn’t gotten far.

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