Environmental genomics approaches for the study of multiple stressors in freshwater ecosystems

目前施加于水生生境的人为压力（金属负荷增加、营养物浓度升高、酸度增加、入侵物种加速引入）可能产生极端环境条件，从而改变受支持的群落并损害这些生态系统的功能。评估多种应激源对水生生态系统的影响尤其具有挑战性，因为应激源之间和生物本身之间的相互作用以及应激后复杂的生态和进化动态。这项工作的长期研究目标是为水生生态系统中多种应激源的研究提供新的综合方法。***我建议结合实验进化（突变积累和中生态实验）和基因组学方法（转录组学、群体遗传学和元编码）以及水蚤作为模式生物来评估水生群落对环境胁迫的反应。通过长期的突变积累实验，我们计划研究在最小选择下繁殖的突变系和在选择下繁殖的分离株的整体转录分化模式。这种方法将使我们能够深入了解塑造基因表达的进化力量。我们将探索环境压力源（重金属）改变突变率以及全球转录模式的程度。通过大型中观实验，结合群体基因组学和元条形码方法，我们将评估遗传多样性和群落组成在强加的环境变化中是如何变化的。我们将在种群水平上探索群落组成发生重大变化之前的遗传变化。此外，中观实验将使我们能够识别对压力源的适应性反应重要的基因。总之，这些研究将为暴露于压力源之间的复杂联系提供前所未有的见解：1)对基因组稳定性的长期影响，2)全球转录模式，3)遗传多样性和群落组成的变化，4)快速反应能力，以及最终5)自然种群的长期健康。***这种独特的实验进化和环境基因组学的结合将使我们的研究小组能够在以前无法达到的细节、控制和复制水平上研究多种压力源对水生生态系统结构和功能属性的影响。拟议的研究也将使我们能够开发和测试新的生态基因组方法来研究多种压力源。拟议的项目为研究生和本科生的多学科和协作培训提供了极好的机会。

The anthropogenic pressures currently applied to aquatic habitats (increased metal loads, high concentrations of nutrients, increased acidity, accelerated introduction of invasive species) can generate extreme environmental conditions that can alter the supported communities and compromise the function of these ecosystems. Evaluating the impact of multiple stressors on aquatic ecosystems is particularly challenging due to the interactions amongst sources of stress and amongst the organisms themselves as well as the complex ecological and evolutionary dynamics that follow after stress. The long-term research objective of the proposed work is to advance new, integrative approaches for the study of multiple stressors in aquatic ecosystems. ***I propose to use a combination of experimental evolution (mutation accumulation and mesocosm experiments) and genomic approaches (transcriptomics, population genetics and metabarcoding) as well as Daphnia as a model organism to evaluate the responses of aquatic communities to environmental stressors. By using a long-term mutation accumulation experiment we plan to examine the global transcritional divergence patterns in mutation lines propagated under minimal selection and in isolates propagated under selection. This approach will allow us to provide insights into the evolutionary forces that shape gene expression. We will explore the extent to which environmental stressors (heavy metals) alter the mutation rate as well as the global transcriptional pattern. By using a large mesocosm experiment coupled with population genomics and metabarcoding approaches we will evaluate how genetic diversity and community composition changes during imposed environmental changes. We will explore the genetic changes at the population level that precede major changes to community composition. Moreover the mesocosm experiment will allow us to identify the genes important for adaptive responses to stressors. Jointly, these studies will provide unprecedented insights into the complex linkages between exposure to stressors and 1) the long-term effects on genome stability, 2) the global transcriptional pattern, 3) the changes in genetic diversity and community composition, 4) the capacity for rapid response, and ultimately 5) the long-term health of natural populations. ***This unique combination of experimental evolution and environmental genomics will allow our research group to investigate the ramifications of multiple stressors on the structural and functional attributes of aquatic ecosystems at a previously unattainable level of detail, control and replication. The proposed studies will also allow us to develop and test new ecological genomic approaches for the study of multiple stressors. The proposed projects provide an excellent opportunity for multidisciplinary and collaborative training at both graduate and undergraduate levels.