What limits the morphological disparity of clades?
What limits the morphological disparity of clades?
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DOI：
10.1098/rsfs.2015.0042
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发表时间：
2015-12
期刊：
影响因子：
4.4
通讯作者：
Jack Oyston;M. Hughes;P. Wagner;S. Gerber;M. Wills
中科院分区：
文献类型：
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作者：
Jack Oyston;M. Hughes;P. Wagner;S. Gerber;M. Wills
主要分支内物种的形态差异在进化过程中表现出多种轨迹模式。然而，有一个显着的趋势，群体达到其最大的差距相对较早的历史，即使他们的物种丰富度或多样性是相对较低的。这种早期高差异的模式表明，有内部的约束（如发育多效性）或外部的限制（如生态竞争）后，可以随后演变的形态多样性。它也已被证明，随着时间的推移，新的字符状态的演变速度下降，在大多数分支（字符饱和），因为没有新的bodyplans和更高的类群的起源率。在这里，我们测试了是否有一个简单的关系之间的水平或速率的字符状态耗尽和形状的一个分支的差异配置文件：具体来说，它的重心（CG）。在93个已灭绝的主要分支的样本中，大多数都表现出一定程度的枯竭，但所有这些都继续进化出新的状态，直到它们灭绝。预测的状态/步骤曲线表明，分支实现了平均60%的推断的最大数量的状态。尽管整体水平的同质性和CG的分支差异配置文件之间的弱，但显着的相关性，有没有显着的关系，我们的任何指标的枯竭曲线形状和分支差异CG。显示早期高差异的分支不太可能比那些在进化后期具有最大差异的分支更早出现特征饱和。
The morphological disparity of species within major clades shows a variety of trajectory patterns through evolutionary time. However, there is a significant tendency for groups to reach their maximum disparity relatively early in their histories, even while their species richness or diversity is comparatively low. This pattern of early high-disparity suggests that there are internal constraints (e.g. developmental pleiotropy) or external restrictions (e.g. ecological competition) upon the variety of morphologies that can subsequently evolve. It has also been demonstrated that the rate of evolution of new character states decreases in most clades through time (character saturation), as does the rate of origination of novel bodyplans and higher taxa. Here, we tested whether there was a simple relationship between the level or rate of character state exhaustion and the shape of a clade's disparity profile: specifically, its centre of gravity (CG). In a sample of 93 extinct major clades, most showed some degree of exhaustion, but all continued to evolve new states up until their extinction. Projection of states/steps curves suggested that clades realized an average of 60% of their inferred maximum numbers of states. Despite a weak but significant correlation between overall levels of homoplasy and the CG of clade disparity profiles, there were no significant relationships between any of our indices of exhaustion curve shape and the clade disparity CG. Clades showing early high-disparity were no more likely to have early character saturation than those with maximum disparity late in their evolution.