Miocene Origin of the Characteristic Broad-Leaved Evergreen Shrub Ammopiptanthus (Leguminosae) in the Desert Flora of Eastern Central Asia
Miocene Origin of the Characteristic Broad-Leaved Evergreen Shrub Ammopiptanthus (Leguminosae) in the Desert Flora of Eastern Central Asia
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DOI：
10.1086/667232
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发表时间：
2012-09
影响因子：
2.3
通讯作者：
Lei Xie;Yong Yang
中科院分区：
文献类型：
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作者：
Lei Xie;Yong Yang
春兰是中亚东部沙漠中唯一的常绿阔叶被子植物属。通过系统发育和分子定年分析研究了Ammopiptanthus的进化历史，并进行了比以往更广泛的采样，以阐明该属的起源和中亚东部的植物区系。采用简约和贝叶斯方法对MatK和nrITS序列进行分析。采用放松时钟模型的贝叶斯测年法估计了水杉的发散时间。基于nrits的系统发育和基于市场的系统发育都得出了相似的结果，即Ammopiptanthus是单系的，是包括苦参和梭梭在内的一个分支的姐妹。在Ammopiptanthus的质体和核DNA区域均检测到低水平的分子变异。该属的两个种不能通过分析加以区分。根据matK数据估计Ammopiptanthus的茎龄为1960万年（Myr； 95%最高后验密度[HPD]: 11.2 ~ 28.2 Myr）， nrITS分析估计其茎龄为21.8 Myr （95% HPD: 13.8 ~ 30.0 Myr）。估计的分化时间支持Ammopiptanthus是阔叶常绿特提斯植物区系的第三纪遗迹属的假设。随着该地区干旱化的加剧，Ammopiptanthus与中亚东部现代沙漠植物群中的其他特征属一起，由于对当地环境的高生态适应能力而能够成功地建立自己，并持续了很长时间。
Ammopiptanthus is the only broad-leaved evergreen angiosperm genus in the deserts of eastern central Asia. Evolutionary history of Ammopiptanthus was examined by means of phylogenetic and molecular dating analyses with a more extensive sampling than ever to shed light on the origin of the genus and the eastern central Asian flora. MatK and nrITS sequences were analyzed using parsimony and Bayesian methods. Divergence time of Ammopiptanthus was estimated using Bayesian dating analyses with relaxed clock model. Both the nrITS-based phylogeny and the matK-based phylogeny gave similar results that Ammopiptanthus is monophyletic and sister to a clade including Sophora and Ammodendron. Low levels of molecular variation were detected in both the plastid and the nuclear DNA regions within Ammopiptanthus. The two species of the genus cannot be distinguished by the analyses. The stem age of Ammopiptanthus was estimated to be 19.6 million years (Myr; 95% highest posterior density [HPD]: 11.2–28.2 Myr) by the matK data and 21.8 Myr (95% HPD: 13.8–30.0 Myr) by nrITS analysis. The estimated divergence time favors the hypothesis that Ammopiptanthus is a Tertiary relic genus descended from the broad-leaved evergreen Tethyan flora. With increasingly intensified aridification of the region, Ammopiptanthus, together with other characteristic genera in the modern desert flora of eastern central Asia, was able to successfully establish themselves because of high ecological capacities in adaptation to local environments and have persisted for a long time.