Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY 11794-5245, USA.
J Evol Biol. 2010 Jun 1;23(6):1261-77. doi: 10.1111/j.1420-9101.2010.01987.x. Epub 2010 Apr 8.
We tested the hypothesis that increased telencephalon size has evolved in threespine stickleback fish (Gasterosteus aculeatus) from structurally complex habitats using field-caught samples from one sea-run (ancestral) and 18 ecologically diverse freshwater (descendant) populations. Freshwater habitats ranged from shallow, structurally complex lakes with benthic-foraging stickleback (benthics), to deeper, structurally simple lakes in which stickleback depend more heavily on plankton for prey (generalists). Contrary to our expectations, benthics had smaller telencephala than generalists, but the shape of the telencephalon of the sea-run and benthic populations were more convex laterally. Convex telencephalon shape may indicate enlargement of the dorsolateral region, which is homologous with the tetrapod hippocampus. Telencephalon morphology is also sexually dimorphic, with larger, less convex telencephala in males. Freshwater stickleback from structurally complex habitats have retained the ancestral telencephalon morphology, but populations that feed more in open habitats on plankton have evolved larger, laterally concave telencephala.
我们通过对来自一个洄游种群（祖先种群）和 18 个生态多样的淡水种群（后代种群）的野外捕获样本进行测试，验证了这样一个假设：即具有复杂结构的栖息地中的三刺鱼（Gasterosteus aculeatus）的端脑体积增大是进化而来的。淡水栖息地范围从具有底栖觅食棘鱼（底栖类）的浅而结构复杂的湖泊，到棘鱼更多地依赖浮游生物作为猎物的更深而结构简单的湖泊（广食类）。与我们的预期相反，底栖类的端脑比广食类小，但洄游种群和底栖类的端脑形状在侧面更凸。凸面的端脑形状可能表明背外侧区域的扩大，该区域与四足动物的海马体同源。端脑形态也存在性别二态性，雄性的端脑更大，侧面更平坦。来自结构复杂栖息地的淡水棘鱼保留了祖先的端脑形态，但在开阔的浮游生物栖息地觅食更多的种群已经进化出更大、侧面凹陷的端脑。
