Evidence for sex-specific selection in brain: a case study of the nine-spined stickleback

Theory predicts that the sex making greater investments into reproductive behaviours demands higher cognitive ability, and as a consequence, larger brains or brain parts. Further, the resulting sexual dimorphism can differ between populations adapted to different environments, or among individuals developing under different environmental conditions. In the nine-spine stickleback (Pungitius pungitius), males perform nest building, courtship, territory defence and parental care, whereas females perform mate choice and produce eggs. Also, predation-adapted marine and competition-adapted pond populations have diverged in a series of ecologically relevant traits, including the level of phenotypic plasticity. Here, we studied sexual dimorphism in brain size and architecture in nine-spined stickleback from marine and pond populations reared in a factorial experiment with predation and food treatments in a common garden experiment. Males had relatively larger brains, larger telencephala, cerebe...理论预言，在繁殖行为中投入更多的性别，其所需的认知能力更高，进而演化出更大的大脑或相应脑区。进一步而言，由此产生的两性异形（sexual dimorphism）会在适应不同环境的种群之间，或是在不同环境条件下发育的个体之间存在差异。在九棘刺鱼（nine-spine stickleback，*Pungitius pungitius*）中，雄性承担筑巢、求偶、领域防御与亲代抚育的职责，而雌性负责配偶选择并产卵。此外，适应捕食压力的海洋种群与适应种间竞争的池塘种群，在一系列生态相关性状上已发生分化，其中包括表型可塑性（phenotypic plasticity）的水平。本研究依托共同花园实验（common garden experiment）体系，设置捕食压力与食物资源的析因实验（factorial experiment）处理组，对来自海洋与池塘种群的九棘刺鱼的脑大小与脑结构两性异形展开了研究。雄性拥有相对更大的大脑、端脑（telencephala）与小脑（cerebe……）