人口增长的动态阶段：了解从瓶颈恢复
Dynamical phases in growing populations: understanding recovery from bottlenecks
摘要：
由于人口规模的急剧下降也通常会改变其组成，人口瓶颈被认为对进化非常重要。然而，尽管具有这种重要意义，但对某一人口瓶颈的影响机制仍然知之甚少。在这种情况下，我们表明，长期后瓶颈的结果可以在很大程度上取决于减少的人口增长的速度，而恢复。也就是说，两个在其他方面相同的人口，每个人都经历了相同的瓶颈，由于瓶颈后增长的不同速度，可能会关注截然不同的人口统计数据。此外，这种行为被证明会随着不同的突变水平而发生非平凡的变化。基本的机制可以追溯到内在的波动，其标准差随着人口规模增长的平方根的倒数而减少。至关重要的是，这种不断减少的波动与基本的动态相结合，并导致不同的（非平衡）人口行为制度，由临界人口规模的突然转变所界定。从这个角度来看，生长和突变通过改变动态阶段的持续时间和特征来改变进化结果;我们推测这一特征可能在许多系统中具有普遍的重要性。
英文摘要：
Since steep declines in a population's size also typically alter its composition, population bottlenecks are considered highly important for evolution. However, despite such significance, the mechanisms governing the impact of a given population bottleneck remain poorly understood. In this context, we show that long-term post-bottleneck outcomes can depend crucially on the rate at which a diminished population grows whilst recovering. That is, two otherwise identical populations, each having undergone the same bottleneck, can fixate on dramatically different demographics due to different rates of post-bottleneck growth. This behaviour is moreover shown to change non-trivially with different levels of mutation. The underlying mechanism can be traced to intrinsic fluctuations whose standard deviation decreases in time with the inverse square root of the growing population size. Crucially, such decreasing fluctuations couple to the underlying dynamics and result in distinct regimes of (non-equilibrium) demographic behaviour, delimited by abrupt transitions at critical population sizes. Seen through this lens, growth and mutation alter evolutionary outcomes by changing the duration and character of dynamical phases; a feature that we speculate may be of generic importance across many systems.
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