Data from: Reversed brain size sexual dimorphism accompanies loss of parental care in white sticklebacks

AbstractUncovering factors that shape variation in brain morphology remains a major challenge in evolutionary biology. Recently, it has been shown that brain size is positively associated with level of parental care behavior in various taxa. One explanation for this pattern is that the cognitive demands of performing complex parental care may require increased brain size. This idea is known as the parental brain hypothesis (PBH). We set out to test the predictions of this hypothesis in wild populations of threespine stickleback (Gasterosteus aculeatus). These fish are commonly known to exhibit (1) uniparental male care and (2) sexual dimorphism in brain size (males>females). To test the PBH, we took advantage of the existence of closely related populations of stickleback that display variation in parental care behavior: common marine threespine sticklebacks (uniparental male care) and white threespine sticklebacks (no care). To begin, we quantified genetic differentiation among two common populations and three white populations from Nova Scotia. We found overall low differentiation among populations, although FST was increased in between-type comparisons. We then measured the brain weights of males and females from all five populations along with two additional common populations from British Columbia. We found that sexual dimorphism in brain size is reversed in white stickleback populations: males have smaller brains than females. Thus, while several alternatives need to be ruled out, the PBH appears to be a reasonable explanation for sexual dimorphism in brain size in threespine sticklebacks., Usage notesBrain weights and SLs of Nova Scotian sticklebacksDryad Brain Data - July 2014.csvSNP Table for Nova Scotian SticklebacksA table of single nucleotide polymorphisms derived from a sample of males from six populations of Nova Scotian sticklebacks. Each row represents a position in the stickleback reference genome, and each column the genotype of an individual fish. See manuscript for population codes.WhiteCommon SNP Table - July 2014.txt

**摘要** 解析塑造脑形态变异的关键因素，仍是演化生物学领域的重大挑战。近期研究表明，在诸多生物类群中，脑容量与亲代抚育行为的强度呈正相关。针对这一规律，一种解释为：执行复杂亲代抚育行为所需的认知负荷，可能需要更大的脑容量。该理论被称为**亲代脑假说（parental brain hypothesis, PBH）**。本研究旨在三刺棘鱼（*Gasterosteus aculeatus*）的野生种群中验证该假说的预测。这类鱼类具有两个典型特征：(1) 单亲雄性抚育行为；(2) 脑容量存在性二态性（雄性脑容量大于雌性）。为验证亲代脑假说，我们利用了亲缘关系相近但亲代抚育行为存在差异的棘鱼种群：普通海洋三刺棘鱼（实行单亲雄性抚育）与白色三刺棘鱼（无亲代抚育行为）。首先，我们对来自新斯科舍省的2个普通棘鱼种群与3个白色棘鱼种群的遗传分化水平进行了量化。结果显示，种群整体遗传分化程度较低，但类群间比较的FST值有所升高。随后，我们测定了上述5个种群以及另外2个来自不列颠哥伦比亚省的普通棘鱼种群的雌雄个体脑重量。研究发现，白色棘鱼种群的脑容量性二态性发生了逆转：雄性脑容量小于雌性。因此，尽管仍需排除若干其他潜在解释，但亲代脑假说似乎可以合理地解释三刺棘鱼脑容量的性二态性现象。

**使用说明**
1. 文件 `Brain weights and SLs of Nova Scotian sticklebacksDryad Brain Data - July 2014.csv`：包含新斯科舍省棘鱼的脑重量与标准体长（standard length, SL）相关数据。
2. 文件 `SNP Table for Nova Scotian Sticklebacks`：基于新斯科舍省6个棘鱼种群的雄性个体样本生成的单核苷酸多态性（single nucleotide polymorphism, SNP）位点表，每一行对应棘鱼参考基因组的一个变异位点，每一列代表一条个体鱼的基因型，种群代码详见研究论文。
3. 文件 `WhiteCommon SNP Table - July 2014.txt`