Department of Biology and Centre for Advanced Research in Environmental Genomics, University of Ottawa, Ontario K1N 6N5, Canada.
Am Nat. 2012 Aug;180(2):270-83. doi: 10.1086/666609. Epub 2012 Jun 19.
Abundant ecological opportunity is thought to drive adaptation and diversification. The presence of multiple opportunities leads to divergent selection, which can slow adaptation when niche-specific beneficial mutations have antagonistically pleiotropic effects. Alternately, competition for multiple opportunities can generate divergent selection, which leads to high rates of adaptive differentiation. Which outcome occurs may depend on the spatial structure of those ecological opportunities. In a mixture of resources, competition for multiple opportunities can drive divergent selection; however, if each resource is available in a spatially distinct patch, simultaneous competition for multiple opportunities cannot occur. We report the effects of the extent and spatial structure of ecological opportunity on the evolutionary dynamics of populations of Pseudomonas fluorescens over 1,000 generations. We varied the extent of ecological opportunity by varying the number of sugar resources (mannose, glucose, and xylose), and we varied spatial structure by providing resources in either mixtures or spatially distinct patches. We saw that a particularly novel resource (xylose) drove the rate of adaptation when provided in a mixture but had no effect on diversity. Instead, we saw the evolution of a single adaptive strategy that differed with respect to phenotype and degree of specialization, depending on both the extent and the spatial structure of ecological opportunity.
丰富的生态机会被认为是驱动适应和多样化的原因。多种机会的存在导致分歧选择，如果特定于生态位的有利突变具有拮抗多效性，那么分歧选择可能会减缓适应。或者，对多种机会的竞争可以产生分歧选择，从而导致高的适应性分化率。哪种结果发生可能取决于这些生态机会的空间结构。在资源混合物中，对多种机会的竞争可以驱动分歧选择；然而，如果每个资源都在空间上不同的斑块中可用，则不可能同时竞争多种机会。我们报告了生态机会的程度和空间结构对 Pseudomonas fluorescens 种群超过 1000 代的进化动态的影响。我们通过改变糖资源（甘露糖、葡萄糖和木糖）的数量来改变生态机会的程度，并且通过在混合物或空间上不同的斑块中提供资源来改变空间结构。我们发现，当提供混合物时，一种特别新颖的资源（木糖）会驱动适应的速度，但对多样性没有影响。相反，我们看到了一种单一的适应性策略的进化，这种策略在表型和专业化程度上有所不同，这取决于生态机会的程度和空间结构。
