Matuszewski Sebastian, Hermisson Joachim, Kopp Michael
Mathematics and BioSciences Group, Faculty of Mathematics, University of Vienna, Oskar-Morgenstern-Platz 1, A-1090, Vienna, Austria.
Evolution. 2014 Sep;68(9):2571-88. doi: 10.1111/evo.12465. Epub 2014 Jul 10.
Fisher's geometric model has been widely used to study the effects of pleiotropy and organismic complexity on phenotypic adaptation. Here, we study a version of Fisher's model in which a population adapts to a gradually moving optimum. Key parameters are the rate of environmental change, the dimensionality of phenotype space, and the patterns of mutational and selectional correlations. We focus on the distribution of adaptive substitutions, that is, the multivariate distribution of the phenotypic effects of fixed beneficial mutations. Our main results are based on an "adaptive-walk approximation," which is checked against individual-based simulations. We find that (1) the distribution of adaptive substitutions is strongly affected by the ecological dynamics and largely depends on a single composite parameter γ, which scales the rate of environmental change by the "adaptive potential" of the population; (2) the distribution of adaptive substitution reflects the shape of the fitness landscape if the environment changes slowly, whereas it mirrors the distribution of new mutations if the environment changes fast; (3) in contrast to classical models of adaptation assuming a constant optimum, with a moving optimum, more complex organisms evolve via larger adaptive steps.
费希尔几何模型已被广泛用于研究多效性和生物体复杂性对表型适应的影响。在此，我们研究费希尔模型的一个版本，其中一个种群适应逐渐变化的最优值。关键参数是环境变化速率、表型空间的维度以及突变和选择相关性的模式。我们关注适应性替代的分布，即固定有益突变的表型效应的多元分布。我们的主要结果基于“适应性行走近似”，并通过基于个体的模拟进行检验。我们发现：（1）适应性替代的分布受到生态动力学的强烈影响，并且在很大程度上取决于单个复合参数γ，该参数通过种群的“适应潜力”来衡量环境变化速率；（2）如果环境变化缓慢，适应性替代的分布反映适应度景观的形状，而如果环境变化迅速，它反映新突变的分布；（3）与假设最优值恒定的经典适应模型相反，在最优值移动的情况下，更复杂的生物体通过更大的适应性步骤进化。
