Establishing a time-scale for plant evolution
Establishing a time-scale for plant evolution
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DOI：
10.1111/j.1469-8137.2011.03794.x
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发表时间：
2011-01-01
期刊：
影响因子：
9.4
通讯作者：
Donoghue, Philip C. J.
中科院分区：
文献类型：
--
作者：
Clarke, John T.;Warnock, Rachel C. M.;Donoghue, Philip C. J.
植物彻底改变了地球，但检验因果关系的假设需要一个可靠的植物进化时间尺度。虽然时钟方法已经得到了广泛的发展，但对化石数据的正确解释和适当实施的关注较少。针对主要陆地植物谱系的模型代表之间的差异，我们构建了17个校准，包括最小约束和软最大约束。使用七个叶绿体基因的数据集，我们进行了交叉验证分析，以确定校准的一致性。然后进行了六个分子时钟分析，一个是原始校准，另一个是探索基节点上的最大值变化和校准中的先验概率密度对发散估计的影响。交叉验证突出了管藻和真叶藻的校准不一致，要么是因为它们的软极大值过于保守，要么是因为没有检测到的速率变化。分子时钟分析给出了冠状胚芽植物的5.68-8.15亿年(Ma)和冠状被子植物的175-240 Ma的估计。我们既拒绝被子植物的后侏罗纪起源，也拒绝后寒武纪陆地植物的起源。我们的分析还表明，主要胚生体谱系的建立速度比大多数先前研究中提出的要慢得多。这些结论与目前的古植物学数据完全一致，尽管不一定与古植物学家的解释一致。
Plants have utterly transformed the planet, but testing hypotheses of causality requires a reliable time-scale for plant evolution. While clock methods have been extensively developed, less attention has been paid to the correct interpretation and appropriate implementation of fossil data.We constructed 17 calibrations, consisting of minimum constraints and soft maximum constraints, for divergences between model representatives of the major land plant lineages. Using a data set of seven plastid genes, we performed a cross-validation analysis to determine the consistency of the calibrations. Six molecular clock analyses were then conducted, one with the original calibrations, and others exploring the impact on divergence estimates of changing maxima at basal nodes, and prior probability densities within calibrations.Cross-validation highlighted Tracheophyta and Euphyllophyta calibrations as inconsistent, either because their soft maxima were overly conservative or because of undetected rate variation. Molecular clock analyses yielded estimates ranging from 568-815 million yr before present (Ma) for crown embryophytes and from 175-240 Ma for crown angiosperms.We reject both a post-Jurassic origin of angiosperms and a post-Cambrian origin of land plants. Our analyses also suggest that the establishment of the major embryophyte lineages occurred at a much slower tempo than suggested in most previous studies. These conclusions are entirely compatible with current palaeobotanical data, although not necessarily with their interpretation by palaeobotanists.