Evolution of brain region volumes during artificial selection for relative brain size

The vertebrate brain shows an extremely conserved layout across taxa. Still, the relative sizes of separate brain regions vary markedly between species. One interesting pattern is that larger brains seem associated with increased relative sizes only of certain brain regions, for instance telencephalon and cerebellum. Till now, the evolutionary association between separate brain regions and overall brain size is based on comparative evidence and remains experimentally untested. Here we test the evolutionary response of brain regions to directional selection on brain size in guppies (Poecilia reticulata) selected for large and small relative brain size. In these animals, artificial selection led to a fast response in relative brain size, while body size remained unchanged. We use micro-CT to investigate how the volumes of 11 main brain regions respond to selection for larger vs. smaller brains. We found no differences in relative brain region volumes between large- and small-brained anima...脊椎动物的脑部结构在各分类群中呈现极强的保守性，但不同物种间各独立脑区的相对体积却存在显著差异。一个有趣的演化现象是，脑总体积更大的物种似乎仅在特定脑区呈现相对体积增大的特征，例如端脑（telencephalon）与小脑（cerebellum）。迄今为止，各脑区与整体脑体积之间的演化关联仅基于比较生物学证据，尚未经实验验证。本研究以经过相对脑体积人工选择的孔雀鱼（Poecilia reticulata）为实验对象，探究脑区对脑体积定向选择的演化响应。在该实验种群中，人工选择使相对脑体积快速产生响应，而个体体型未发生改变。我们利用显微计算机断层扫描（micro-CT）技术，探究11个主要脑区的体积如何响应脑体积增大与减小的选择压力。研究发现，高脑体积组与低脑体积组的动物在各脑区相对体积上未出现显著差异……