Key Laboratory of Biodiversity and Biogeography, Plant Germplasm and Genomics Center, Germplasm Bank of Wild Species, Chinese Academy of Sciences, Kunming 650204, China.
Mol Phylogenet Evol. 2010 Aug;56(2):675-89. doi: 10.1016/j.ympev.2010.02.018. Epub 2010 Feb 18.
The evolution of the eastern Asian and eastern North American disjunction of the witch-hazel genus Hamamelis L. (Hamamelidaceae) was examined through phylogenetic and biogeographic analyses. Phylogenetic relationships of all Hamamelis species were reconstructed using parsimony and Bayesian analyses of sequence data from six plastid (trnL-F, psaA-ycf3, rps16, matK, atpB-rbcL, and psbA-trnH) and two nuclear (ITS and ETS) DNA regions. The phylogeny was then used to infer the biogeographic origin and subsequent diversification using both event-based (DIVA) and maximum likelihood (LAGRANGE) methods incorporating fossil data. The times of divergence within Hamamelis were estimated with the Bayesian approach using the program BEAST. A very low level of molecular variation was detected in both the plastid and the nuclear DNA regions within Hamamelis. The combined analyses resulted in a phylogeny of the genus with higher resolution and support values. Hamamelis was supported to be monophyletic with H. mollis from eastern China diverged first in the genus. All North American species formed a clade and was sister to the eastern Asian H. japonica. Within the North American clade, H. mexicana was sister to H. vernalis, and the recently described species H. ovalis was found to be closely related to the widespread species H. virginiana. The stem age of Hamamelis was estimated to be at the Eocene (51.2 mya, with 95% HDP: 49.0-54.6 mya), and the crown age of the genus was dated to be at the late Miocene (9.7 mya, with 95% HDP: 3.6-18.1 mya, or 10.6 mya, with 95% HDP: 4.2-19.6 mya). The disjunction between the eastern Asian and the eastern North American species was dated to be 7.1 mya (95% HDP: 3.1-13.6 mya) or 7.7 mya (95% HDP: 3.4-13.6 mya). Biogeographic analyses incorporating fossils resulted in more equally possible solutions at the stem lineage of Hamamelis than those including extant species only. Eastern Asia is inferred to be the most-likely area for the origin of Hamamelis. The current disjunction was due to the extinction in western North America and Europe from Eocene to late Miocene, and later migration from eastern Asia into North America. The Bering land bridge was hypothesized to have played an important role in the evolution of this disjunction. The current species diversity of the genus was the result of relatively recent diversification events during the late Miocene rather than long accumulation of lineages from the early Tertiary.
通过系统发育和生物地理分析，研究了东亚和北美东部金缕梅属（金缕梅科）的间断分布。利用来自六个质体（trnL-F、psaA-ycf3、rps16、matK、atpB-rbcL 和 psbA-trnH）和两个核（ITS 和 ETS）DNA 区域的序列数据，通过简约法和贝叶斯分析重建了所有金缕梅物种的系统发育关系。然后，使用基于事件的（DIVA）和最大似然（LAGRANGE）方法，结合化石数据，从生物地理起源和随后的多样化两个方面推断系统发育关系。使用程序 BEAST 通过贝叶斯方法估计了金缕梅属内的分歧时间。在金缕梅属的质体和核 DNA 区域均检测到非常低水平的分子变异。联合分析得到了一个分辨率和支持值更高的属系统发育。金缕梅被支持为单系，其中中国东部的 H. mollis 首先在属中分化。所有北美物种形成一个分支，与东亚的 H. japonica 为姐妹群。在北美分支内，H. mexicana 与 H. vernalis 为姐妹群，最近描述的物种 H. ovalis 与广泛分布的 H. virginiana 关系密切。金缕梅的茎干年龄估计为始新世（51.2 mya，95% HDP：49.0-54.6 mya），属的冠层年龄为中新世晚期（9.7 mya，95% HDP：3.6-18.1 mya，或 10.6 mya，95% HDP：4.2-19.6 mya）。东亚和北美东部物种的间断发生在 7.1 mya（95% HDP：3.1-13.6 mya）或 7.7 mya（95% HDP：3.4-13.6 mya）。生物地理分析结合化石得出的金缕梅属茎干谱系的可能解决方案比仅包含现生物种的解决方案更为均衡。东亚被推断为金缕梅属起源的最有可能的区域。目前的间断是由于始新世到晚中新世期间北美西部和欧洲的灭绝，以及后来从东亚向北美迁移的结果。白令陆桥被假设在这一分化过程中发挥了重要作用。该属目前的物种多样性是中新世晚期相对较新的多样化事件的结果，而不是早期第三纪的谱系长期积累的结果。
