The limits of evolutionary adaptation in ecological time: experimental evolution and ecology.

我的研究项目使用实验室实验来研究生态学和进化论的基本过程。单细胞酵母菌和藻类的种群很容易在实验室中维护，凭借其非常大的体积(一个小烧瓶中有数十亿个个体)和快速的周转(几个小时的世代时间)，它们使实时研究大规模过程成为可能。我将利用这些实验室的缩影来研究三种过程。第一个项目通过展示如何在短时间内进化出截然不同的生活方式来探索适应的局限性。我将追溯一系列的修饰，使通过光合作用在光线下生长的藻类(如绿色植物)进化为可以在完全黑暗中生长的类型，使用有机化学物质作为食物来源(如真菌)。第二个项目是研究适应的特殊性。不同的细菌或酵母菌株可以各自代谢一定范围的底物，就像动物只消耗有限范围的食物一样。我将记录当酵母种群被提供一种复杂的底物混合物时，它们的饮食是如何演变的，比如它们在自然环境中遇到的。这些实验的目的是证明，在实验室人群中进化的饮食专业化程度可以根据涉及代谢途径结构的生化原理来预测。第三个项目将实验方法扩展到整个社区，以发现他们如何应对严重的压力。这引入了两种新技术。第一种是通过扩散的梯度选择，通过不断适应不断增加的压力水平，逐步形成一个抗性群落。第二种是蓄积式生物反应器，它的设计目的是在自然群落中发现能够执行某些特定任务的非常罕见的类型，例如降解特定的毒素。这些技术既可以应用于社区组装的基本过程，也可以应用于实际问题，如受污染的土壤和水的生物修复。

My research program uses laboratory experiments to investigate fundamental processes in ecology and evolution. Populations of unicellular yeasts and algae are easily maintained in the laboratory, and by virtue of their very large size (billions of individuals in a small flask) and rapid turnover (generation times of a few hours) they make it possible to study large-scale processes in real time. I shall use these laboratory microcosms to study three kinds of process. The first project explores the limits of adaptation by showing how radically different ways of life can evolve within short periods of time. I shall trace the series of modifications that enable an alga that grows in the light by photosynthesis (like a green plant) to evolve into types that can grow in complete darkness, using an organic chemical as a food source (like a fungus). The second project investigates the specificity of adaptation. Different strains of bacteria or yeast can each metabolize a certain range of substrates, just as animals consume only a limited range of foodstuffs. I will document how diet of yeast populations evolves when they are offered a complex mixture of substrates, such as they encounter in natural environments. The goal of these experiments is to show that the degree of dietary specialization that evolves in laboratory populations can be predicted from biochemical principles involving the structure of metabolic pathways. The third project extends the experimental approach to whole communities to discover how they can respond to severe stress. This introduces two novel techniques. The first is gradient selection with dispersal, which contrives the gradual emergence of a resistant community by successive adaptation to increasing levels of stress. The second is the accumulating bioreactor, which is designed to discover very rare types in natural communities that are capable of performing some defined task, such as degrading a particular toxin. These techniques can be applied both to fundamental processes of community assembly and to practical problems such as the bioremediation of polluted soil and water.