Data from: Quantitative genetic analysis of brain size variation in sticklebacks: support for the mosaic model of brain evolution

The mosaic model of brain evolution postulates that different brain regions are relatively free to evolve independently from each other. Such independent evolution is possible only if genetic correlations among the different brain regions are less than unity. We estimated heritabilities, evolvabilities and genetic correlations of relative size of the brain and its different regions in the three-spined stickleback (Gasterosteus aculeatus). We found that heritabilities were low (average h2 = 0.24), suggesting a large plastic component to brain architecture. However, evolvabilities of different brain parts were moderate, suggesting the presence of additive genetic variance to sustain a response to selection in the long term. Genetic correlations among different brain regions were low (average rg = 0.40) and significantly less than unity. These results, along with those from analyses of phenotypic and genetic integration, indicate a high degree of independence between different brains regions, suggesting that responses to selection are unlikely to be severely constrained by genetic and phenotypic correlations. Hence, the results give strong support for the mosaic model of brain evolution. However, the genetic correlation between brain and body size was high (rg = 0.89), suggesting a constraint for independent evolution of brain and body size in sticklebacks.大脑进化镶嵌模型（mosaic model of brain evolution）提出，不同脑区能够相对独立地各自演化。该独立演化模式的成立前提为：不同脑区间的遗传相关度小于1。本研究以三刺鱼（Gasterosteus aculeatus）为研究对象，估算了整体大脑及其不同脑区相对体积的遗传力、可演化性与遗传相关度。结果显示，遗传力普遍偏低（平均h²=0.24），表明大脑结构存在较强的可塑性成分。不过，不同脑区的可演化性处于中等水平，提示存在可长期维持选择响应的加性遗传方差。不同脑区间的遗传相关度普遍偏低（平均rg=0.40），且显著小于1。上述结果结合表型与遗传整合分析的结果，表明不同脑区间存在高度的独立性，提示选择响应不太可能受到遗传与表型相关度的严重制约。因此，本研究结果为大脑进化镶嵌模型提供了强有力的支持。然而，大脑体积与躯体体积间的遗传相关度较高（rg=0.89），提示三刺鱼的大脑与躯体体积的独立演化存在一定制约。