Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Mol Syst Biol. 2012;8:621. doi: 10.1038/msb.2012.54.
Competition between species is a major ecological force that can drive evolution. Here, we test the effect of this force on the evolution of cooperation within a species. We use sucrose metabolism of budding yeast, Saccharomyces cerevisiae, as a model cooperative system that is subject to social parasitism by cheater strategies. We find that when cocultured with a bacterial competitor, Escherichia coli, the frequency of cooperator phenotypes in yeast populations increases dramatically as compared with isolated yeast populations. Bacterial competition stabilizes cooperation within yeast by limiting the yeast population density and also by depleting the public goods produced by cooperating yeast cells. Both of these changes induced by bacterial competition increase the cooperator frequency because cooperator yeast cells have a small preferential access to the public goods they produce; this preferential access becomes more important when the public good is scarce. Our results indicate that a thorough understanding of species interactions is crucial for explaining the maintenance and evolution of cooperation in nature.
物种间的竞争是一种主要的生态力量，可以推动进化。在这里，我们测试了这种力量对物种内合作进化的影响。我们使用出芽酵母（Saccharomyces cerevisiae）的蔗糖代谢作为模型合作系统，该系统易受到欺骗策略的社会寄生虫的影响。我们发现，与孤立的酵母种群相比，当与细菌竞争者大肠杆菌共培养时，酵母种群中合作者表型的频率会急剧增加。细菌竞争通过限制酵母种群密度和消耗合作酵母细胞产生的公共资源来稳定酵母内的合作。细菌竞争引起的这两种变化都增加了合作者的频率，因为合作者酵母细胞对它们产生的公共资源有优先获取的优势；当公共资源稀缺时，这种优先获取变得更加重要。我们的结果表明，深入了解物种间的相互作用对于解释自然界中合作的维持和进化至关重要。
