Evolution of diversity

根据达尔文的说法，多样性的起源是谜团中的奥秘。今天有数以百万计的物种存在，但产生这种多样性的详细机制仍然不清楚。传统的物种形成模式建立在地理隔离的基础上：如果祖先谱系的亚种群在地理上变得细分(例如，由于气候变化而碎片化)，它们就会走上不同的进化轨迹，从而实现多样化。在这里，划分基因库的初始过程是不适应的。相比之下，在适应性物种形成过程中，基因库的分裂本身就是一种适应。过去十年，人们对这种适应性多元化的兴趣与日俱增，因为经验和理论研究都证明了它的可行性。进化分支的典范理论普及了多样化可以由生态互动推动的概念，例如对资源的竞争。使用细菌E.Coli，我开发了一个微生物模型系统，以测试进化分支导致的适应性多样化理论。大肠杆菌提供了许多优势，包括有可能将其进化到数千代人，并通过冻结中间阶段来创造化石记录。由于碳资源的竞争，我们进化中的大肠杆菌种群经历了多样化。本研究以分子、生理和生态学实验为基础，全面分析了该模型系统中适应性多样化过程的各个方面，记录了多样化事件发生前、发生中和发生后的进化变化。我们还在研究不同微生物系统中多样性的起源，在这个系统中，多样化是在一般合作问题的背景下发生的，导致在生产有益物质的过程中合作者和作弊者共存。我们研究的另一个主要焦点是基于个体的反应动力学对我们的实验模型系统进行数学建模，利用我们从实验中获得的知识来描述个体的生长、繁殖和生存。最后，我们计划在实验和数学模型系统中研究捕食如何影响多样化。

The origin of diversity is the mystery of mysteries according to Darwin. Millions of species exist today, but the detailed mechanisms generating this diversity are still unclear. The traditional model of speciation is based on geographical isolation: if subpopulations of an ancestral lineage become geographically subdivided (e.g. through fragmentation due to climatic changes), they embark on different evolutionary trajectories, and hence diversify. Here the initial process of splitting the gene pool is not adaptive. In contrast, in the process of adaptive speciation, the splitting of the gene pool is itself an adaptation. The past decade has seen growing interest in such adaptive diversification, because both empirical and theoretical studies have documented its feasibility. The paradigmatic theory of evolutionary branching has popularized the notion that diversification can be driven by ecological interactions such as competition for resources. Using the bacterium E. coli, I have developed a microbial model system to test the theory of adaptive diversification due to evolutionary branching. E. coli offers many advantages, including the possibility of evolving it for thousands of generations and creating a fossil record by freezing intermediate stages. Our evolving E. coli populations have undergone diversification due to competition for carbon resources. Based on molecular, physiological and ecological experiments, my research aims at fully analyzing all aspects of the process of adaptive diversification in this model system, documenting the evolutionary changes prior, during and after the diversification event. We are also studying the origins of diversity in a different microbial system, in which diversification occurs in the context of the general problem of cooperation, leading to coexistence of cooperators and cheaters in the production of a beneficial substance. Another main focus of our research is the mathematical modeling of our experimental model systems based on "reaction kinetics" of individuals, describing individual growth, reproduction and survival using the knowledge gained from our experiments. Finally, we plan to investigate how predation affects diversification in both the experimental and the mathematical model systems.