Genetic architecture supports mosaic brainevolution and independent brain–bodysize regulation

摘要

The mammalian brain consists of distinct parts that fulfil different functions. Finlay andDarlington have argued that evolution of the mammalian brain is constrained bydevelopmental programs, suggesting that different brain parts are not free to respondindividually to selection and evolve independent of other parts or overall brain size. However,comparisons among mammals with matched brain weights often reveal greater differencesin brain part size, arguing against strong developmental constraints. Here we test thesehypotheses using a quantitative genetic approach involving over 10,000 mice. We identifyindependent loci for size variation in seven key parts of the brain, and observe that brain partsshow low or no phenotypic correlation, as is predicted by a mosaic scenario. We also demonstratethat variation in brain size is independently regulated from body size. The allometric relationsseen at higher phylogenetic levels are thus unlikely to be the product of strong developmentalconstraints.