Predator-driven brain size evolution in natural populations of Trinidadian killifish (Rivulus hartii)

Vertebrates exhibit extensive variation in relative brain size. It has long been assumed that this variation is the product of ecologically driven natural selection. Yet, despite more than 100 years of research, the ecological conditions that select for changes in brain size are unclear. Recent laboratory selection experiments showed that selection for larger brains is associated with increased survival in risky environments. Such results lead to the prediction that increased predation should favour increased brain size. Work on natural populations, however, foreshadows the opposite trajectory of evolution; increased predation favours increased boldness, slower learning, and may thereby select for a smaller brain. We tested the influence of predator-induced mortality on brain size evolution by quantifying brain size variation in a Trinidadian killifish, Rivulus hartii, from communities that differ in predation intensity. We observed strong genetic differences in male (but not female) br...脊椎动物（Vertebrates）的相对脑容量（relative brain size）存在广泛变异。长期以来，学界普遍认为此类变异系生态驱动的自然选择（ecologically driven natural selection）的产物。然而，尽管已有百余年的研究积累，可筛选出脑容量演化改变的生态条件仍未明晰。近期的实验室选择实验显示，针对更大脑容量的选择与危险环境中存活率的提升呈显著关联。此类研究结果催生了一项预测：捕食压力的增加应会驱动脑容量增大。但针对自然种群的研究则指向相反的演化轨迹；捕食压力提升会筛选出更大胆、学习更迟缓的个体，进而可能倾向于选择更小的脑容量。我们以捕食强度存在差异的特立尼达底鳉（Rivulus hartii）种群为研究对象，通过量化其脑容量变异，检验了捕食者诱导的死亡率对脑容量演化的影响。我们观测到雄性（而非雌性）存在显著的遗传差异……