Data from: Exposure to predators does not lead to the evolution of larger brains in experimental populations of threespine stickleback

AbstractNatural selection is often invoked to explain differences in brain size among vertebrates. However, the particular agents of selection that shape brain size variation remain obscure. Recent studies suggest that predators may select for larger brains because increased cognitive and sensory abilities allow prey to better elude predators. Yet, there is little direct evidence that exposure to predators causes the evolution of larger brains in prey species. We experimentally tested this prediction by exposing families of 1000-2000 F2 hybrid benthic-limnetic threespine stickleback to predators under naturalistic conditions, along with matched controls. After two generations of selection, we found that fish from the predator addition treatment had significantly smaller brains (specifically smaller telencephalons and optic lobes) than fish from the control treatment. After an additional generation of selection, we reared experimental fish in a common environment and found that this difference in brain size was maintained in the offspring of fish from the predator addition treatment. Our results provide direct experimental evidence that (a) predators can indeed drive the evolution of brain size – but not in the fashion commonly expected and (b) that the tools of experimental evolution can be used to the study the evolution of the vertebrate brain., Usage notesExperimental pond brain size measurementsMeasurements of the size of four different parts of the brain in threespine sticklebacks collected from experimental ponds. See readme for complete breakdown of columns etc.experimental_pond_brain_size_samuk_et_al_2018.txtCommon garden brain size measurementsMeasurements of the size of four different parts of the brain in threespine sticklebacks collected from experimental ponds as fry and reared in a common laboratory environment. See readme for complete breakdown of columns etc.common_garden_brain_size_samuk et_al_2018.txt

摘要
自然选择常被用于阐释脊椎动物间脑容量的差异。然而，塑造脑容量变异的具体选择动因仍不甚明晰。近期研究表明，捕食者可能会倾向于选择脑容量更大的猎物——因为更高的认知与感官能力能让猎物更好地躲避捕食者。然而，目前鲜有直接证据表明，暴露于捕食者压力会促使猎物物种演化出更大的脑容量。我们通过在自然模拟环境下，将1000~2000个家系的F₂代杂交底栖-浮游型三棘刺鱼（threespine stickleback）暴露于捕食者压力下，并设置匹配对照组，以此对该预测进行实验验证。经过两代选择后，我们发现，添加捕食者处理组的鱼类脑容量（具体为端脑（telencephalon）与视叶（optic lobe））显著小于对照组鱼类。在额外增加一代选择后，我们将实验鱼置于统一环境中饲养，发现捕食者处理组鱼类的后代仍保留了脑容量的差异。我们的研究结果提供了直接的实验证据：（a）捕食者确实能够推动脑容量的演化——但并非学界普遍预期的方式；（b）实验演化（experimental evolution）手段可用于研究脊椎动物脑的演化。

使用说明
实验池塘脑容量测量：本数据集包含从实验池塘中采集的三棘刺鱼的4个脑区的尺寸测量数据。列信息等完整细节请参阅readme文件。数据文件：experimental_pond_brain_size_samuk_et_al_2018.txt
同质园（common garden）脑容量测量：本数据集包含从实验池塘采集的幼体三棘刺鱼，经统一实验室环境饲养后的4个脑区的尺寸测量数据。列信息等完整细节请参阅readme文件。数据文件：common_garden_brain_size_samuk_et_al_2018.txt