Collaborative Research: A Molecular Investigation of Trade-Offs and Evolutionary Stability in a Simple Competitive Ecosystem

9629695迪恩两个竞争物种，每一个都是单一可替代资源的赢家，当两种资源都可用时，可能会共存。 这两个物种是否会出现同域分化，各自专注于自己喜欢的资源，还是一个物种会进化取代另一个物种？ 由于突变是一个随机过程，许多人认为种群的适应性分化是不可复制的：如果生命的磁带是可复制的，进化的结果将是截然不同的。 Dean和Dykhuizen博士建议使用克隆细菌的复制种群来实验性地区分这些假设。 因为这些菌株在遗传上几乎是相同的，所以同域物种形成的生态学问题与通过权衡而进化出专门化的遗传学问题是一致的。 第一部分建立了两株E.大肠杆菌中有两个不同的乳糖操纵子，竞争两个可选择的半乳糖苷。 这项研究将测试的预测，从生物化学的知识（自下而上的方法），这两种菌株将共存，只有在一定范围内的比例的两个替代半乳糖苷。 第二部分探讨了共存的演化动力学。 长期恒化器实验（自上而下的方法）将允许适应性突变在每个菌株中积累。 这些实验旨在解决：1）在分子水平上的权衡是否迫使特定资源的专业化;以及2）增加专业化（或增加泛化）是否会扰乱初始平衡频率或导致竞争性排斥（即只有一种菌株获胜）。

9629695 Dean Two competing species, each a winner on a single substitutable resource, may coexist when both resources are available. Will there be a sympatric divergence of the two species, each specializing on its preferred resource, or will one evolve to replace the other? Because mutation is a stochastic process, many believe that the adaptive divergence of populations is irreproducible: if the tape of life is rerun, the evolutionary outcome will be dramatically different. Drs. Dean and Dykhuizen propose to distinguish these hypotheses experimentally using replicated populations of clonal bacteria. Because the strains are almost genetically identical, the ecological question of sympatric speciation becomes congruent with the genetic question of the evolution of specialization through trade-offs. Part 1 will establish two strains of E. coli harboring two different lactose operons and competing for two alternative galactosides. This study will test the prediction, made from a knowledge of biochemistry (a bottom up approach), that the two strains will coexist only within a certain range of ratios of the two alternative galactosides. Part 2 investigates the evolutionary dynamics of coexistence. Long-term chemostat experiments (a top-down approach) will allow adaptive mutations to accumulate in each strain. These experiments are designed to address: 1) whether trade-offs at the molecular level force specialization on particular resources; and, 2) whether increasing specialization (or increasing generalization) perturbs the initial equilibrium frequencies or leads to competitive exclusion (i.e. only one strain wins).