Sustained fitness gains and variability in fitness trajectories in the long-term evolution experiment with Escherichia coli.
Sustained fitness gains and variability in fitness trajectories in the long-term evolution experiment with Escherichia coli.
复制标题
在大肠杆菌的长期进化实验中，适应性轨迹的持续健身和适应性轨迹的可变性。
DOI：
10.1098/rspb.2015.2292
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发表时间：
2015-12-22
期刊：
影响因子：
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通讯作者：
Hajela N
中科院分区：
文献类型：
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作者：
Lenski RE;Wiser MJ;Ribeck N;Blount ZD;Nahum JR;Morris JJ;Zaman L;Turner CB;Wade BD;Maddamsetti R;Burmeister AR;Baird EJ;Bundy J;Grant NA;Card KJ;Rowles M;Weatherspoon K;Papoulis SE;Sullivan R;Clark C;Mulka JS;Hajela N
Many populations live in environments subject to frequent biotic and abiotic changes. Nonetheless, it is interesting to ask whether an evolving population's mean fitness can increase indefinitely, and potentially without any limit, even in a constant environment. A recent study showed that fitness trajectories of Escherichia coli populations over 50 000 generations were better described by a power-law model than by a hyperbolic model. According to the power-law model, the rate of fitness gain declines over time but fitness has no upper limit, whereas the hyperbolic model implies a hard limit. Here, we examine whether the previously estimated power-law model predicts the fitness trajectory for an additional 10 000 generations. To that end, we conducted more than 1100 new competitive fitness assays. Consistent with the previous study, the power-law model fits the new data better than the hyperbolic model. We also analysed the variability in fitness among populations, finding subtle, but significant, heterogeneity in mean fitness. Some, but not all, of this variation reflects differences in mutation rate that evolved over time. Taken together, our results imply that both adaptation and divergence can continue indefinitely—or at least for a long time—even in a constant environment.
