弱突变极限下鞍点控制的适应度景观上大种群默认演化模式的标点平衡
Punctuated equilibrium as the default mode of evolution of large populations on fitness landscapes dominated by saddle points in the weak-mutation limit
摘要：
间断平衡（英语：Punctuated equilibrium）是一种进化模式，在这种模式中，表型变化以快速爆发的方式发生，这些爆发被更长的停滞间隔所分隔，在此期间突变积累，但没有发生主要的表型变化。间断平衡最初是在古生物学框架内提出的，以解释化石记录中典型的过渡形式的缺乏。从理论上讲，间断平衡与自组织临界性（SOC）有关，自组织临界性是一种模型，在该模型中，演化系统中雪崩的大小是幂律分布的，导致重大事件越来越罕见。我们在这里表明，在弱突变限制下，一个大的人口将花费大部分时间在适应度景观的鞍点附近的停滞。当一个新的有益突变被固定在进化的种群中时，停滞期会被快速转变打断，这种转变在lnNe时间（Ne，有效种群大小）内进行，种群会移动到不同的鞍点，或者在更罕见的情况下，从鞍点移动到局部峰值。因此，间断平衡是在不涉及SOC或其他特殊条件的简单模型下的默认进化模式。
英文摘要：
Punctuated equilibrium is a mode of evolution in which phenetic change occurs in rapid bursts that are separated by much longer intervals of stasis during which mutations accumulate but no major phenotypic change occurs. Punctuated equilibrium has been originally proposed within the framework of paleobiology, to explain the lack of transitional forms that is typical of the fossil record. Theoretically, punctuated equilibrium has been linked to self-organized criticality (SOC), a model in which the size of avalanches in an evolving system is power-law distributed, resulting in increasing rarity of major events. We show here that, under the weak-mutation limit, a large population would spend most of the time in stasis in the vicinity of saddle points in the fitness landscape. The periods of stasis are punctuated by fast transitions, in lnNe time (Ne, effective population size), when a new beneficial mutation is fixed in the evolving population, which moves to a different saddle, or on much rarer occasions, from a saddle to a local peak. Thus, punctuated equilibrium is the default mode of evolution under a simple model that does not involve SOC or other special conditions.
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