Limits to Evolutionary Adaptation of Phytoplankton in the Arctic Ocean

全球变暖正在迅速改变海洋温度，pH值，碳饱和状态，循环和氧化状态，这将影响浮游植物的群落组成;世界海洋的主要生产者。要预测哪些海洋浮游植物物种将在这些不断变化的环境条件下持续存在并占主导地位，就需要了解这些物种的适应性进化潜力。通过这个项目，我们将提高对极地海洋浮游植物群落，特别是硅藻的动态的理解和预测能力，以及它们对全球变暖导致的环境变化的适应能力的限制。浮游植物作为单细胞微生物，种群规模大，繁殖率高，具有快速适应环境变化的巨大潜力。这可以通过（i）个体生物通过表观遗传过程（即表型可塑性）适应其表型，（ii）通过作用于个体基因型的自然选择，以及（iii）群体选择（即谱系和物种分选）来实现。这三个基本水平的选择分别导致生理、种群遗传组成和群落结构的变化，这反过来又可以驱动生物地球化学循环和更高营养水平的变化。这些适应性变化已经发生在北冰洋，但现有的气候模型未能捕捉到这些结合生态和进化的适应性反应。该提案旨在通过研究极地硅藻模式物种-圆柱拟脆藻以及北冰洋10种硅藻物种-的基因组、表观基因组和转录组一级的适应性进化，填补这一根本性知识空白。因此，我们将讨论环境变化，如北冰洋海冰的丧失将如何影响主要初级生产者的适应性进化和多样性，并对受到全球变暖极端威胁的生态系统中的生物地球化学循环产生影响。

Global warming is rapidly altering ocean temperature, pH, carbon saturation state, circulation, and oxidation state, and this will impact the community composition of phytoplankton; the primary producers in the world's oceans. Predicting which marine phytoplankton species will persist and dominate under these changing environmental conditions requires an understanding of the adaptive evolutionary potential of these species. With this project, we will improve understanding and predictive capability of the dynamics of polar marine phytoplankton communities, especially diatoms, and the limits of their adaptive capacities in response to environmental change driven by global warming. As single-celled microbes with large population sizes and high replication rates, phytoplankton species have considerable potential to adapt rapidly to changing environmental conditions. This can happen by (i) individual organisms adapting their phenotypes through epigenetic processes (i.e. phenotypic plasticity), (ii) by natural selection acting on individual genotypes, and by (iii) group selection (i.e. lineage and species-sorting). These three fundamental levels of selection result in changes in physiology, population genetic composition and community structure, respectively, which in turn can drive changes in both biogeochemical cycles and higher trophic levels. These adaptive changes already occur in the Arctic Ocean, yet existing climate models fail to capture these combined ecological and evolutionary adaptive responses. This proposal aims to address this fundamental gap in knowledge by studying adaptive evolution at the level of the genome, epigenome and transcriptome of a model species for polar diatoms, Fragilariopsis cylindrus, as well as 10 diatom species from the Arctic Ocean. We will thus address how environmental changes such as the loss of sea ice in the Arctic Ocean will impact the adaptive evolution and diversity of key primary producers with consequences for biogeochemical cycles in an ecosystem that is under extreme threat by global warming.