Interplay of population size and environmental fluctuations: A new explanation for fitness cost rarity in asexuals,Ecology Letters

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Interplay of population size and environmental fluctuations: A new explanation for fitness cost rarity in asexuals
Ecology Letters ( IF 7.6 ) Pub Date : 2021-06-18 , DOI: 10.1111/ele.13831
Yashraj Chavhan ₁ , Sarthak Malusare ₁ , Sutirth Dey ₁

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Theoretical models of ecological specialisation commonly assume that adaptation to one environment leads to fitness reductions (costs) in others. However, experiments often fail to detect such costs. We addressed this conundrum using experimental evolution with Escherichia coli in several constant and fluctuating environments at multiple population sizes. We found that in fluctuating environments, smaller populations paid significant costs, but larger ones avoided them altogether. Contrastingly, in constant environments, larger populations paid more costs than the smaller ones. Overall, large population sizes and fluctuating environments led to cost avoidance only when present together. Mutational frequency distributions obtained from whole-genome whole-population sequencing revealed that the primary mechanism of cost avoidance was the enrichment of multiple beneficial mutations within the same lineage. Since the conditions revealed by our study for avoiding costs are widespread, it provides a novel explanation of the conundrum of why the costs expected in theory are rarely detected in experiments.

中文翻译：

人口规模和环境波动的相互作用：无性恋者健身成本稀有的新解释

生态专业化的理论模型通常假设对一种环境的适应会导致其他环境的适应度降低（成本）。然而，实验往往无法检测到这样的成本。我们使用大肠杆菌的实验进化解决了这个难题在多种人口规模的几个恒定和波动的环境中。我们发现，在波动的环境中，较小的种群付出了巨大的代价，而较大的种群则完全避免了它们。相比之下，在恒定的环境中，较大的人口比较小的人口支付更多的成本。总体而言，庞大的人口规模和波动的环境只有在共同存在时才能避免成本。从全基因组全种群测序获得的突变频率分布表明，成本规避的主要机制是同一谱系内多个有益突变的富集。由于我们的研究揭示的避免成本的条件很普遍，它为为什么理论上预期的成本很少在实验中检测到的难题提供了一种新的解释。

更新日期：2021-08-10

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