CAREER: How do mixotroph phenotypic plasticity and adaptive evolution constrain climate feedbacks?

在海洋中，浮游生物进行光合作用从大气中去除二氧化碳，而浮游生物从捕获的猎物中呼吸碳，将二氧化碳返回到大气中。一种叫做混合营养体的特殊浮游生物结合了两种形式的新陈代谢，同时具有植物和动物的功能。由于混合营养体对每个过程的依赖程度取决于环境条件，因此很难预测它们对碳循环的净影响。在不断变化的环境中尤其如此。例如，随着地球表面海洋温度的升高，混合营养体可能会做出塑性（通过其生理状态的可逆改变）和快速进化的反应。这个项目结合了数学模型和实验室实验来验证这样一个假设，即更多的表型可塑性混合营养体不会进化得那么快，因为它们固有的代谢灵活性会降低自然选择的强度。该项目还支持旨在扩大参与和提高数学素养的培训和外联活动。项目人员将培训K-12教师，为博物馆游客提供教育课程，并在数学和生物学的交叉领域进行本科教学。本科生还将领导独立的研究项目，并开发科学教育模块，让高中生量化温度对生物学的影响。作为项目的一部分，博士后和本科生研究人员接受培训和专业发展。为了将混合营养表型的可塑性和进化与气候反馈联系起来，研究人员正在将实验与数学模型相结合。一些来自嗜色单胞菌属的混合营养基因型将被表型化，一个子集将被实验进化以测试它们的适应性进化能力。研究人员正在测量进化谱系中光合作用和吞噬作用的速率，以量化对碳循环的影响，基因组和转录组测序被用来确定适应的分子基础。将开发一系列数学模型来了解塑性和进化的机制基础，并将这些机制与它们的气候影响联系起来。首先，研究人员使用细胞投资模型将经验结果与混合营养体最佳塑性和进化策略的预测进行对比。经过验证的模型模块正在被纳入上层海洋全球生态系统模型，以了解这些策略如何在未来气候情景下改变混合营养盐丰度和对碳循环的贡献。该奖项的资金由生物海洋学和海洋教育项目提供。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In the ocean, plankton that do photosynthesis remove carbon dioxide from the atmosphere, while plankton that respire carbon from captured prey return carbon dioxide to the atmosphere. One special type of plankton called mixotrophs combine both forms of metabolism, functioning as both plant and animal simultaneously. Because the extent to which mixotrophs rely on each process depends on environmental conditions, it can be difficult to predict their net impact on the carbon cycle. This is especially true in changing environments. For example, as Earth’s surface ocean temperatures increase, mixotrophs may respond both plastically (through reversible modifications of their physiological state) and through rapid evolution. This project combines mathematical models and laboratory experiments to test the hypothesis that more phenotypically plastic mixotrophs will not evolve as rapidly because their inherent metabolic flexibility will reduce the strength of natural selection. The project also supports training and outreach designed to broaden participation and expand math literacy. Project personnel will train K-12 teachers, provide educational programs for museum visitors, and conduct undergraduate teaching at the intersection of mathematics and biology. Undergraduate trainees will also lead independent research projects and develop science education modules that allow high school students to quantify the effects of temperature on biology. Postdoctoral and undergraduate researchers receive training and professional development as part of the project.To link mixotroph phenotypic plasticity and evolution to climate feedbacks, researchers are integrating experiments with mathematical models. A number of mixotroph genotypes from the genus Ochromonas will be phenotyped, and a subset will be experimentally evolved to test their capacity for adaptive evolution. Researchers are measuring rates of photosynthesis and phagotrophy in evolved lineages to quantify impacts on the carbon cycle, and genome and transcriptome sequencing are being used to identify the molecular basis of adaptation. A series of mathematical models will be developed to understand the mechanistic bases of plasticity and evolution, and to connect these mechanisms to their climate impacts. First, researchers use a model of cellular investments to contrast empirical results with predictions of mixotrophs’ optimal plastic and evolved strategies. Validated model modules is being incorporated into upper ocean global ecosystem models to understand how these strategies change mixotroph abundance and contributions to the carbon cycle under future climate scenarios.Funds for this award are provided by the Biological Oceanography and Ocean Education Programs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.