Melo Diogo, Marroig Gabriel
Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Sao Paulo, SP 05508-090, Brazil
Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Sao Paulo, SP 05508-090, Brazil.
Proc Natl Acad Sci U S A. 2015 Jan 13;112(2):470-5. doi: 10.1073/pnas.1322632112. Epub 2014 Dec 29.
Modularity is a central concept in modern biology, providing a powerful framework for the study of living organisms on many organizational levels. Two central and related questions can be posed in regard to modularity: How does modularity appear in the first place, and what forces are responsible for keeping and/or changing modular patterns? We approached these questions using a quantitative genetics simulation framework, building on previous results obtained with bivariate systems and extending them to multivariate systems. We developed an individual-based model capable of simulating many traits controlled by many loci with variable pleiotropic relations between them, expressed in populations subject to mutation, recombination, drift, and selection. We used this model to study the problem of the emergence of modularity, and hereby show that drift and stabilizing selection are inefficient at creating modular variational structures. We also demonstrate that directional selection can have marked effects on the modular structure between traits, actively promoting a restructuring of genetic variation in the selected population and potentially facilitating the response to selection. Furthermore, we give examples of complex covariation created by simple regimes of combined directional and stabilizing selection and show that stabilizing selection is important in the maintenance of established covariation patterns. Our results are in full agreement with previous results for two-trait systems and further extend them to include scenarios of greater complexity. Finally, we discuss the evolutionary consequences of modular patterns being molded by directional selection.
模块性是现代生物学中的一个核心概念，为在许多组织层面上研究生物体提供了一个强大的框架。关于模块性，可以提出两个核心且相关的问题：模块性最初是如何出现的，以及哪些力量负责维持和/或改变模块模式？我们利用定量遗传学模拟框架来探讨这些问题，基于先前在双变量系统中获得的结果并将其扩展到多变量系统。我们开发了一个基于个体的模型，该模型能够模拟由许多位点控制的许多性状，这些位点之间具有可变的多效性关系，并在经历突变、重组、漂变和选择的种群中表达。我们使用这个模型来研究模块性出现的问题，从而表明漂变和稳定选择在创建模块变异结构方面效率低下。我们还证明定向选择可以对性状之间的模块结构产生显著影响，积极促进所选种群中遗传变异的重组，并可能促进对选择的响应。此外，我们给出了由定向选择和稳定选择相结合的简单机制产生的复杂协变的例子，并表明稳定选择在维持已建立的协变模式方面很重要。我们的结果与先前关于双性状系统的结果完全一致，并进一步将其扩展到包括更复杂的情况。最后，我们讨论了由定向选择塑造的模块模式的进化后果。
