Evolutionary Responses to Global Changes in Salinity and Temperature

全球水循环的剧烈变化和冰融化的增加正在导致北部沿海海域变新鲜。盐度的降低和温度的升高可能会共同减少河口和海洋生物的数量。数据表明，降低盐度和高温都会增加能量消耗，降低普通桡足动物的存活率和繁殖能力。本项目将研究盐度降低和温度升高对野生affinis种群进化反应的共同影响，以及在实验室的选择实验中。这项研究将为生物对气候变化的响应提供新的见解，因为没有研究分析盐度和温度对进化响应的共同影响，而且相对较少的研究研究了盐度下降的影响。一般来说，选择是如何在整个基因组水平上起作用的还不是很清楚，特别是对于非模式生物。作为一种优势的河口桡足类动物，与鲑鱼、鲱鱼和凤尾鱼一样，是维持北半球沿海食物网和渔业的最重要物种之一。因此，深入了解其对气候变化的进化反应对渔业的可持续性和粮食安全具有重要意义。两名来自历史上代表性不足的群体的研究生将在这个项目中接受培训。该项目将带来额外的社会效益，包括为K-12学生开发教育模块和国际合作。本研究将解决以下问题：(1)种群对盐度和温度变化的响应程度，以及适应性和生理成本是什么？(2)种群如何响应盐度-温度相互作用的影响？(3)野生种群是否表现出对盐度和温度的自然选择？为了分析亲和沙蚕种群对盐度和温度耦合影响的进化响应，研究者将进行实验室选择实验和野生种群基因组调查。选择实验是确定适应速度、轨迹和极限的有力工具。在实验室选择过程中，将研究适应性相关性状和基因组表达的进化转变，以及低盐度和高温选择机制下选择的基因组特征。研究人员还将对生活在圣劳伦斯海和波罗的海沿盐度和温度梯度的亲和鲈种群进行种群基因组测序，并确定显示选择特征的基因。该项目将确定在野生种群中显示出选择特征的位点是否与在实验室选择中受到青睐的位点相同。这种可重复性将提供更大的信心，即参与适应盐度和/或温度的基因已被捕获。

Drastic changes in the global water cycle and increases in ice melt are causing the freshening of Northern coastal seas. The combination of both reduced salinity and increased temperature will likely act in concert to reduce populations of estuarine and marine organisms. Data indicate that reduced salinity and high temperature would each increase the energy costs as well as reduce survival and reproduction of the common copepod Eurytemora affinis. This project will examine the joint effects of salinity reduction and temperature increase on the evolutionary responses of populations of E. affinis in the wild, as well as in selection experiments in the laboratory. This study will provide novel insights into responses of organisms to climate change, as no study has analyzed the joint impacts of salinity and temperature on evolutionary responses, and relatively few studies have examined the impacts of declining salinity. In general, how selection acts at the whole genome level is not well understood, particularly for non-model organisms. As a dominant estuarine copepod, E. affinis is among the most important species sustaining coastal food webs and fisheries in the Northern Hemisphere, such as salmon, herring, and anchovy. Thus, insights into its evolutionary responses with changing climate have important implications for sustainability of fisheries and food security. Two graduate students from historically underrepresented groups will be trained during this project. The project will have additional societal benefits, including development of educational modules for K-12 students and international collaboration. This study will address the following questions: (1) To what extent could populations evolve in response to salinity and temperature change, and what are the fitness and physiological costs? (2) How will populations respond to the impacts of salinity-temperature interactions? (3) Do wild populations show evidence of natural selection in response to salinity and temperature? To analyze the evolutionary responses of E. affinis populations to the coupled impacts of salinity and temperature, the investigator will perform laboratory selection experiments and population genomic surveys of wild populations. Selection experiments constitute powerful tools for determining the rate, trajectory, and limits of adaptation. During laboratory selection, evolutionary shifts in fitness-related traits and genomic expression will be examined, as well as genomic signatures of selection in response to low salinity and high temperature selection regimes. The investigator will also conduct population genomic sequencing of E. affinis populations that reside along salinity and temperature gradients in the St. Lawrence and Baltic Sea, and identify genes that show signatures of selection. The project will determine whether the loci that show signatures of selection in the wild populations are the same as those favored during laboratory selection. This reproducibility will provide greater confidence that the genes involved in adaptation to salinity and/or temperature have been captured.