Keck Graduate Institute of Applied Life Sciences, Claremont, CA 91711, USA.
Proc Biol Sci. 2012 Jan 22;279(1727):247-56. doi: 10.1098/rspb.2011.0870. Epub 2011 Jun 22.
Evolutionary adaptation is often likened to climbing a hill or peak. While this process is simple for fitness landscapes where mutations are independent, the interaction between mutations (epistasis) as well as mutations at loci that affect more than one trait (pleiotropy) are crucial in complex and realistic fitness landscapes. We investigate the impact of epistasis and pleiotropy on adaptive evolution by studying the evolution of a population of asexual haploid organisms (haplotypes) in a model of N interacting loci, where each locus interacts with K other loci. We use a quantitative measure of the magnitude of epistatic interactions between substitutions, and find that it is an increasing function of K. When haplotypes adapt at high mutation rates, more epistatic pairs of substitutions are observed on the line of descent than expected. The highest fitness is attained in landscapes with an intermediate amount of ruggedness that balance the higher fitness potential of interacting genes with their concomitant decreased evolvability. Our findings imply that the synergism between loci that interact epistatically is crucial for evolving genetic modules with high fitness, while too much ruggedness stalls the adaptive process.
进化适应常常被比作爬山或登顶。在突变相互独立的适应度景观中，这个过程很简单，但突变（上位性）之间的相互作用以及影响多个性状的基因座（多效性）在复杂和现实的适应度景观中至关重要。我们通过研究在 N 个相互作用的基因座模型中无性单倍体生物（单倍型）群体的进化，研究了上位性和多效性对适应性进化的影响，其中每个基因座与 K 个其他基因座相互作用。我们使用一种替代之间上位性相互作用的定量度量方法，发现它是 K 的递增函数。当单倍型以高突变率适应时，在进化枝上观察到的上位性替代对比预期更多。在具有中等崎岖度的景观中可以达到最高的适应性，这种景观平衡了相互作用基因的更高适应性潜力与其相应的降低的可进化性。我们的发现意味着，相互作用的基因座之间的协同作用对于进化具有高适应性的遗传模块至关重要，而过多的崎岖度会阻碍适应性进化过程。
