Data from: Spatial structure of ecological opportunity drives adaptation in a bacterium

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 leading 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, competition for multiple opportunities simultaneously cannot occur. We report the effects of extent and spatial structure of ecological opportunity on the evolutionary dynamics of populations of Pseudomonas fluorescens over 1000 generations. We varied extent of ecological opportunity by varying the number of sugar resources (mannose, glucose, and xylose), and 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 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 spatial structure of ecological opportunity.

学界普遍认为，充足的生态机会（ecological opportunity）可推动适应性演化与物种多样化。多重生态机会的存在会引发歧向选择；当生态位特异性有益突变存在拮抗多效性效应时，该选择会减缓适应性演化进程。反之，对多重生态机会的竞争亦可催生歧向选择，进而带来极高的适应性分化速率。最终出现何种演化结果，或许取决于这些生态机会的空间结构。在资源混合的环境中，对多重生态机会的竞争可引发歧向选择；但若每种资源均分布于空间分隔的斑块中，则无法同时出现对多重生态机会的竞争。本研究探讨了生态机会的规模与空间结构对1000代演化周期内荧光假单胞菌（Pseudomonas fluorescens）种群演化动力学的影响。我们通过调整糖类资源的种类数（甘露糖、葡萄糖与木糖）来调控生态机会的规模，并通过将资源设置为混合分布或空间分隔斑块两种方式，改变实验的空间结构。实验结果显示，一种极具新颖性的资源（木糖）在资源混合环境中会提升适应性演化速率，但对种群多样性无显著影响。与之相反，我们观察到仅演化出单一的适应性策略，该策略的表型与特化程度均会随生态机会的规模与空间结构发生变化。