Conducting assisted evolution in a threatened coral species for promoting more resilient reef ecosystems in the face of climate change

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Coral reefs serve as reservoirs of biodiversity and are essential for the maintenance of healthy ecosystems. However, as a result of continued detrimental anthropogenic effects and natural events linked to climate change, it is feared that the intensity and complexity of environmental changes are overwhelming the intrinsic ability of corals to adapt and survive. As a possible solution for increasing coral resiliency and for promoting the long-term survival of reef ecosystems, I am proposing a study for using human-assisted evolution and selective breeding to accelerate naturally-occurring evolutionary processes in order to enhance key tolerance traits. Performing intraspecific crosses using resilient genotypes is one method for rapidly generating even more robust genotypes because sexual reproduction can combine multiple beneficial alleles into a single genome and therefore generate fitter genotypes faster. Moreover, utilizing sexually-reproducing corals offers access to millions of propagules, thereby increasing the potential for experimental testing, for estimating the heritability of traits crucial for adaptation to climate change, and for producing large numbers of individuals that can be reared for restoration efforts. Specifically, I am proposing to perform the first experimental investigation of selective breeding in a threatened and ecologically-important coral species, Acropora cervicornis, in order to test the hypothesis that crossing temperature and disease resilient genotypes can generate offspring that are more robust in terms of thermotolerance and disease resistance under current and/or projected environmental conditions. I will measure, over time, a suite of physiological responses as proxies for fitness and from these data determine the heritability of thermotolerance and disease resilience, which is crucial for evaluating adaptive potential. I will also compare differential gene expression during ambient and stressful conditions over time in order to identify the molecular pathways contributing to coral resilience. Then I will conduct fitness assays to test for trade-offs to pH tolerance, as selection on trait(s) can lead to negative fitness consequences for other traits. With increasing ocean acidification resulting in lower seawater pH values, pH tolerance is also an important trait to consider. Finally, I will select a range of robust genotypes for conducting field trials and place them in the same offshore nursery where the parental genotypes are housed to monitor, in-situ, their growth and survival over time. The results of this study will have far-reaching implications as the data from the heritability and gene expression analyses will be useful for basic sciences research since trait heritabilities are largely unknown for most coral species. Additionally, if selective breeding proves successful, this method may be adapted to other species and regions and ultimately help to advance coral restoration strategies worldwide.