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

珊瑚礁是生物多样性的蓄水池，对维持健康的生态系统至关重要。然而，由于与气候变化有关的持续有害的人为影响和自然事件，人们担心环境变化的强度和复杂性正在压倒珊瑚适应和生存的内在能力。作为提高珊瑚复原力和促进珊瑚礁生态系统长期生存的可能解决方案，我提议进行一项研究，利用人类辅助进化和选择性繁殖来加速自然发生的进化过程，以增强关键的耐受性特征。利用弹性基因进行种内杂交是一种快速产生更健壮的基因类型的方法，因为有性繁殖可以将多个有益的等位基因结合到单个基因组中，从而更快地产生更合适的基因类型。此外，利用具有有性繁殖能力的珊瑚提供了获得数百万繁殖珊瑚的途径，从而增加了进行实验测试、估计对适应气候变化至关重要的特征的遗传力以及产生大量可供恢复工作饲养的个体的可能性。具体地说，我提议对一种受威胁的、具有生态重要性的珊瑚物种进行首次选择性繁殖的实验研究，以检验这样一种假设，即杂交温度和抗病基因可以产生在当前和/或预计的环境条件下更耐热和更抗病的后代。随着时间的推移，我将测量一系列生理反应，作为健康的替代指标，并根据这些数据确定耐热性和疾病复原力的遗传性，这对评估适应潜力至关重要。我还将随着时间的推移比较环境和压力条件下的差异基因表达，以确定有助于珊瑚弹性的分子途径。然后，我将进行适合度分析，以测试对pH耐受性的权衡，因为对性状的选择(S)可能会导致其他性状的负面适合度结果。随着海洋酸化的加剧导致海水的pH值降低，对pH的耐受性也是一个需要考虑的重要特征。最后，我将选择一系列健壮的基因类型进行田间试验，并将它们放在相同的离岸苗圃中，在那里饲养双亲基因，以原位监测它们随时间的生长和存活。这项研究的结果将具有深远的影响，因为遗传力和基因表达分析的数据将有助于基础科学研究，因为大多数珊瑚物种的特征遗传力在很大程度上是未知的。此外，如果选择性繁殖被证明是成功的，这种方法可能适用于其他物种和地区，并最终有助于推进全球珊瑚恢复战略。

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.