Brain structure evolution in a basal vertebrate clade: evidence from phylogenetic comparative analysis of cichlid fishes.
Brain structure evolution in a basal vertebrate clade: evidence from phylogenetic comparative analysis of cichlid fishes.
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DOI：
10.1186/1471-2148-9-238
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发表时间：
2009-09-21
影响因子：
3.4
通讯作者：
Kolm N
中科院分区：
文献类型：
--
作者：
Gonzalez-Voyer A;Winberg S;Kolm N
脊椎动物的大脑由几个相互关联、功能截然不同的结构组成，围绕这些结构是如何进化的这个基本问题进行了很多争论。一方面，根据“马赛克进化假说”，由于脑组织新陈代谢成本的增加，人们期望选择特定的结构来调节被看好的认知能力。另一方面，“协同进化假说”认为，发育限制限制了这种马赛克进化，整个大脑的大小会随着对其任何组成部分的选择而变化。到目前为止，对这些大脑进化假说的分析仅限于哺乳动物和鸟类；不包括基本的和最多样化的脊椎动物类别放线鸟。利用最近开发的系统发育多变量异速生长分析和可以识别不同进化速度的比较方法的组合，即使在高度相关的特征中，我们研究了高度可变的鱼鳍鱼的脑部结构进化；总脑大小解释了慈鱼脑结构体积变化的86%，低于之前报道的哺乳动物的比例。大脑结构在配对异速生长中表现出差异，这表明在进化过程中大小的变化具有一定程度的独立性。这一结果得到了不同结构之间在异速生长分析的主尺寸轴上其载荷强度的差异的支持。进化速度分析普遍支持多变量异速生长分析的结果，表明几种结构在进化模式上存在差异。研究发现，嗅球和下丘脑的进化速度比其他结构快，而背髓的进化速度最慢。我们的结果支持大脑进化的马赛克模型，因为某些结构是以模块化的方式进化的，在慈鱼中协同进化的影响很小，但不可忽视。有趣的是，在慈鱼体内呈现不同进化模式的结构之一，嗅球，也被证明与哺乳动物的其他结构进化不同。因此，我们对基本脊椎动物分支的结果也指向了所有脊椎动物保守的发展计划。
The vertebrate brain is composed of several interconnected, functionally distinct structures and much debate has surrounded the basic question of how these structures evolve. On the one hand, according to the 'mosaic evolution hypothesis', because of the elevated metabolic cost of brain tissue, selection is expected to target specific structures mediating the cognitive abilities which are being favored. On the other hand, the 'concerted evolution hypothesis' argues that developmental constraints limit such mosaic evolution and instead the size of the entire brain varies in response to selection on any of its constituent parts. To date, analyses of these hypotheses of brain evolution have been limited to mammals and birds; excluding Actinopterygii, the basal and most diverse class of vertebrates. Using a combination of recently developed phylogenetic multivariate allometry analyses and comparative methods that can identify distinct rates of evolution, even in highly correlated traits, we studied brain structure evolution in a highly variable clade of ray-finned fishes; the Tanganyikan cichlids. Total brain size explained 86% of the variance in brain structure volume in cichlids, a lower proportion than what has previously been reported for mammals. Brain structures showed variation in pair-wise allometry suggesting some degree of independence in evolutionary changes in size. This result is supported by variation among structures on the strength of their loadings on the principal size axis of the allometric analysis. The rate of evolution analyses generally supported the results of the multivariate allometry analyses, showing variation among several structures in their evolutionary patterns. The olfactory bulbs and hypothalamus were found to evolve faster than other structures while the dorsal medulla presented the slowest evolutionary rate. Our results favor a mosaic model of brain evolution, as certain structures are evolving in a modular fashion, with a small but non-negligible influence of concerted evolution in cichlid fishes. Interestingly, one of the structures presenting distinct evolutionary patterns within cichlids, the olfactory bulbs, has also been shown to evolve differently from other structures in mammals. Hence, our results for a basal vertebrate clade also point towards a conserved developmental plan for all vertebrates.
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