Data from: Temporally autocorrelated environmental fluctuations inhibit the evolution of stress tolerance

As global environmental conditions continue to change at an unprecedented rate many species will experience increases in natural and anthropogenic stress. Generally speaking, selection is expected to favor adaptations that reduce the negative impact of environmental stress (i.e., stress tolerance). However, natural environmental variables typically fluctuate, exhibiting various degrees of temporal autocorrelation, known as environmental 'colors,' which may complicate evolutionary responses to stress. Here we combine experiments and theory to show that temporal environmental autocorrelation can determine long-term evolutionary responses to stress, without affecting the total amount of stress experienced over time. Experimental evolution of RNA virus lineages in differing environmental autocorrelation treatments agreed closely with predictions from our theoretical models that stress tolerance is favored in less autocorrelated (whiter) environments but disfavored in more autocorrelated ('redder)ned' environments. This is explained by an interaction between environmental color autocorrelation and a phenotypic tradeoff between stress tolerance and reproductive ability. The degree to which environmental color autocorrelation influences evolutionary trajectories depends on the shape of this tradeoff as well as the relative level of tolerance exhibited by novel mutants. These results suggest that long-term evolutionary dynamics depend not only on the overall strength of selection, but also on the way that selection is distributed over time.随着全球环境以史无前例的速率持续变化，众多物种面临的自然胁迫与人为胁迫（anthropogenic stress）均会加剧。一般而言，自然选择会倾向于那些能够降低环境胁迫负面影响的适应性性状，即胁迫耐受性（stress tolerance）。然而，自然环境变量通常会随时间波动，并呈现出不同程度的时间自相关（temporal autocorrelation），这类现象被称为环境"色彩"，其可能会使物种对胁迫的进化响应变得更为复杂。本研究结合实验与理论方法，证实环境的时间自相关能够决定物种对胁迫的长期进化响应，且不会改变物种在整个周期内所经历的总胁迫量。在不同环境自相关处理条件下开展的RNA病毒谱系（RNA virus lineages）实验进化（experimental evolution）结果，与本研究理论模型的预测高度吻合：即在时间自相关性更低的（更"白"的）环境中，胁迫耐受性会受到自然选择的青睐，而在时间自相关性更高的（更"红"的）环境中则会被抑制。这一现象可通过环境色彩（时间自相关）与胁迫耐受性和繁殖能力之间的表型权衡（phenotypic tradeoff）之间的互作关系得到解释。环境色彩（时间自相关）对进化轨迹的影响程度，取决于该表型权衡的形状，以及新型突变体所表现出的耐受性相对水平。上述研究结果表明，物种的长期进化动态不仅取决于自然选择的整体强度，还取决于选择在时间维度上的分布模式。