Turner Caroline B, Marshall Christopher W, Cooper Vaughn S
Microbiology and Molecular Genetics University of Pittsburgh Pittsburgh Pennsylvania.
Evol Lett. 2018 Aug 4;2(4):355-367. doi: 10.1002/evl3.75. eCollection 2018 Aug.
Evolution experiments have demonstrated high levels of genetic parallelism between populations evolving in identical environments. However, natural populations evolve in complex environments that can vary in many ways, likely sharing some characteristics but not others. Here, we ask whether shared selection pressures drive parallel evolution across distinct environments. We addressed this question in experimentally evolved populations founded from a clone of the bacterium . These populations evolved for 90 days (approximately 600 generations) under all combinations of high or low carbon availability and selection for either planktonic or biofilm modes of growth. Populations that evolved in environments with shared selection pressures (either level of carbon availability or mode of growth) were more genetically similar to each other than populations from environments that shared neither characteristic. However, not all shared selection pressures led to parallel evolution. Genetic parallelism between low-carbon biofilm and low-carbon planktonic populations was very low despite shared selection for growth under low-carbon conditions, suggesting that evolution in low-carbon environments may generate stronger trade-offs between biofilm and planktonic modes of growth. For all environments, a population's fitness in a particular environment was positively correlated with the genetic similarity between that population and the populations that evolved in that particular environment. Although genetic similarity was low between low-carbon environments, overall, evolution in similar environments led to higher levels of genetic parallelism and that genetic parallelism, in turn, was correlated with fitness in a particular environment.
进化实验表明，在相同环境中进化的种群之间存在高度的遗传平行性。然而，自然种群是在复杂的环境中进化的，这些环境可能在许多方面有所不同，可能共享一些特征，但并非其他特征。在这里，我们要问的是，共享的选择压力是否会驱动不同环境中的平行进化。我们在由一种细菌的克隆体建立的实验进化种群中解决了这个问题。这些种群在高碳或低碳可用性的所有组合以及浮游或生物膜生长模式的选择下进化了90天（约600代）。在具有共享选择压力（碳可用性水平或生长模式）的环境中进化的种群，彼此之间的遗传相似性高于那些既不共享碳可用性水平也不共享生长模式的环境中的种群。然而，并非所有共享的选择压力都会导致平行进化。尽管在低碳条件下生长有共享选择，但低碳生物膜种群和低碳浮游种群之间的遗传平行性非常低，这表明在低碳环境中的进化可能会在生物膜和浮游生长模式之间产生更强的权衡。对于所有环境，一个种群在特定环境中的适应性与该种群与在该特定环境中进化的种群之间的遗传相似性呈正相关。虽然低碳环境之间的遗传相似性较低，但总体而言，在相似环境中的进化导致了更高水平的遗传平行性，而这种遗传平行性反过来又与在特定环境中的适应性相关。
