Evolution of diversity

在达尔文看来，生物多样性的起源是奥秘中的奥秘。今天存在着数以百万计的物种，但产生这种多样性的详细机制仍然不清楚。传统的物种形成模型是基于地理隔离的：如果一个祖先谱系的亚种群在地理上被细分（例如，由于气候变化造成的碎片化），它们就会走上不同的进化轨迹，从而实现多样化。在这里，分裂基因库的初始过程是不适应的。相反，在适应性物种形成的过程中，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样化的兴趣越来越大，因为实证和理论研究都证明了它的可行性。进化分支的范式理论已经普及了多样化可以由生态相互作用（如资源竞争）驱动的概念。利用大肠杆菌，我开发了一个微生物模型系统来测试由于进化分支而产生的适应性多样化理论。大肠杆菌有很多优势，包括进化数千代的可能性，以及通过冷冻中间阶段创造化石记录。由于对碳资源的竞争，我们不断进化的大肠杆菌种群经历了多样化。基于分子、生理和生态实验，我的研究旨在全面分析该模型系统中适应性多样化过程的各个方面，记录多样化事件发生前、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，其中多样化是在一般合作问题的背景下发生的，导致合作者和骗子在生产有益物质时共存。我们研究的另一个主要重点是基于个体“反应动力学”的实验模型系统的数学建模，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.