Arnold Sommerfeld Center for Theoretical Physics (ASC) and Center for NanoScience (CeNS), Department of Physics, Ludwig-Maximilians-Universität München, Theresienstrasse 37, D-80333 München, Germany.
Sci Rep. 2012;2:281. doi: 10.1038/srep00281. Epub 2012 Feb 21.
Microbes providing public goods are widespread in nature despite running the risk of being exploited by free-riders. However, the precise ecological factors supporting cooperation are still puzzling. Following recent experiments, we consider the role of population growth and the repetitive fragmentation of populations into new colonies mimicking simple microbial life-cycles. Individual-based modeling reveals that demographic fluctuations, which lead to a large variance in the composition of colonies, promote cooperation. Biased by population dynamics these fluctuations result in two qualitatively distinct regimes of robust cooperation under repetitive fragmentation into groups. First, if the level of cooperation exceeds a threshold, cooperators will take over the whole population. Second, cooperators can also emerge from a single mutant leading to a robust coexistence between cooperators and free-riders. We find frequency and size of population bottlenecks, and growth dynamics to be the major ecological factors determining the regimes and thereby the evolutionary pathway towards cooperation.
尽管存在被搭便车者利用的风险，但提供公共物品的微生物在自然界中广泛存在。然而，支持合作的确切生态因素仍令人费解。在最近的实验之后，我们考虑了种群增长和种群重复分裂成新殖民地的作用，这种分裂模拟了简单的微生物生命周期。基于个体的建模揭示了人口波动，它导致殖民地组成的巨大差异，从而促进了合作。由于种群动态的偏差，这种波动导致了在重复分裂成群体时，两种截然不同的稳定合作的机制。首先，如果合作水平超过一个阈值，合作者将接管整个种群。其次，合作者也可以从一个单一的突变体中出现，从而在合作者和搭便车者之间形成稳定的共存。我们发现种群瓶颈的频率和大小，以及增长动态是决定机制的主要生态因素，从而决定了合作的进化途径。
