Department of Biological Sciences, Smith College, Northampton, MA, USA.
Department of Genetics, Harvard Medical School, Boston, MA, USA.
Glob Chang Biol. 2019 Oct;25(10):3294-3304. doi: 10.1111/gcb.14764. Epub 2019 Aug 10.
Climate change threatens organisms in a variety of interactive ways that requires simultaneous adaptation of multiple traits. Predicting evolutionary responses requires an understanding of the potential for interactions among stressors and the genetic variance and covariance among fitness-related traits that may reinforce or constrain an adaptive response. Here we investigate the capacity of Acropora millepora, a reef-building coral, to adapt to multiple environmental stressors: rising sea surface temperature, ocean acidification, and increased prevalence of infectious diseases. We measured growth rates (weight gain), coral color (a proxy for Symbiodiniaceae density), and survival, in addition to nine physiological indicators of coral and algal health in 40 coral genets exposed to each of these three stressors singly and combined. Individual stressors resulted in predicted responses (e.g., corals developed lesions after bacterial challenge and bleached under thermal stress). However, corals did not suffer substantially more when all three stressors were combined. Nor were trade-offs observed between tolerances to different stressors; instead, individuals performing well under one stressor also tended to perform well under every other stressor. An analysis of genetic correlations between traits revealed positive covariances, suggesting that selection to multiple stressors will reinforce rather than constrain the simultaneous evolution of traits related to holobiont health (e.g., weight gain and algal density). These findings support the potential for rapid coral adaptation under climate change and emphasize the importance of accounting for corals' adaptive capacity when predicting the future of coral reefs.
气候变化以多种相互作用的方式威胁着生物，这需要同时适应多种特征。预测进化反应需要了解压力之间的相互作用的潜力，以及与适应相关的特征的遗传方差和协方差，这些特征可能加强或限制适应反应。在这里，我们研究了造礁珊瑚 Acropora millepora 适应多种环境压力的能力：海平面上升、海洋酸化和传染性疾病的流行增加。我们测量了生长率（体重增加）、珊瑚颜色（共生藻密度的代表）和存活率，以及在暴露于这三种单一和组合压力源的 40 个珊瑚遗传体中珊瑚和藻类健康的九个生理指标。单一压力源导致了预期的反应（例如，珊瑚在细菌挑战后出现病变，在热应激下白化）。然而，当所有三种压力源结合在一起时，珊瑚并没有遭受更多的伤害。不同压力源之间也没有观察到权衡；相反，在一种压力源下表现良好的个体在其他压力源下也往往表现良好。对特征之间遗传相关性的分析显示出正协方差，这表明对多种压力的选择将加强而不是限制与整个共生体健康相关的特征（例如，体重增加和藻类密度）的同时进化。这些发现支持了珊瑚在气候变化下快速适应的潜力，并强调了在预测珊瑚礁未来时考虑珊瑚适应能力的重要性。
