Department of Systematic Botany, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden;
Am J Bot. 2005 Oct;92(10):1737-48. doi: 10.3732/ajb.92.10.1737.
A molecular dating of the phylogenetically basal eudicots (Ranunculales, Proteales, Sabiales, Buxales and Trochodendrales sensu Angiosperm Phylogeny Group II) has been performed using several fossils as minimum age constraints. All rbcL sequences available in GenBank were sampled for the taxa in focus. Dating was performed using penalized likelihood, and results were compared with nonparametric rate smoothing. Fourteen eudicot fossils, all with a Cretaceous record, were included in this study for age constraints. Nine of these are assigned to basal eudicots and the remaining five taxa represent core eudicots. Our study shows that the choice of methods and fossil constraints has a great impact on the age estimates, and that removing one single fossil change the results in the magnitude of tens of million years. The use of several fossil constraints increase the probability of approaching the true ages. Our results suggest a rapid diversification during the late Early Cretaceous, with all the lineages of basal eudicots emerging during the latest part of the Early Cretaceous. The age of Ranunculales was estimated to 120 my, Proteales to 119 my, Sabiales to 118 my, Buxales to 117 my, and Trochodendrales to 116 my.
已经使用几个化石作为最小年龄限制对系统发育上基础的真双子叶植物（毛茛目、胡椒目、杨柳目、榆目和铁青树目，按照被子植物系统发育分组 II）进行了分子定年。关注的分类群中所有可用的 rbcL 序列都在 GenBank 中进行了采样。使用罚似然法进行了定年，并且将结果与非参数速率平滑进行了比较。本研究包含了 14 个具有白垩纪记录的真双子叶植物化石，作为年龄限制。其中有 9 个被分配到基础真双子叶植物，其余 5 个代表核心真双子叶植物。我们的研究表明，方法和化石限制的选择对年龄估计有很大影响，并且去除一个化石就会导致数千万年的变化。使用多个化石限制可以增加接近真实年龄的可能性。我们的结果表明，在早白垩世晚期发生了快速多样化，所有基础真双子叶植物的谱系都在早白垩世的最后阶段出现。毛茛目的年龄估计为 1.2 亿年，胡椒目的年龄估计为 1.19 亿年，杨柳目的年龄估计为 1.18 亿年，榆目的年龄估计为 1.17 亿年，铁青树目的年龄估计为 1.16 亿年。
