Lang Ping, Dane Fenny, Kubisiak Thomas L, Huang Hongwen
Department of Horticulture, Auburn University, Auburn, AL, USA.
Mol Phylogenet Evol. 2007 Apr;43(1):49-59. doi: 10.1016/j.ympev.2006.07.022. Epub 2006 Aug 26.
The genus Castanea (Fagaceae) is widely distributed in the deciduous forests of the Northern Hemisphere. The striking similarity between the floras of eastern Asia and those of eastern North America and the difference in chestnut blight resistance among species has been of interest to botanists for a century. To infer the biogeographical history of the genus, the phylogeny of Castanea was estimated using DNA sequence data from different regions of the chloroplast genome. Sequencing results support the genus Castanea as a monophyletic group with Castanea crenata as basal. The three Chinese species form a strongly supported sister clade to the North American and European clade. A unique westward expansion of extant Castanea species is hypothesized with Castanea originating in eastern Asia, an initial diversification within Asia during the Eocene followed by intercontinental dispersion and divergence between the Chinese and the European/North American species during the middle Eocene and a split between the European and the North American species in the late Eocene. The differentiation within North America and China might have occurred in early or late Miocene. The North America species are supported as a clade with C. pumila var. ozarkensis, the Ozark chinkapin, as the basal lineage, sister to the group comprising C. pumila var. pumila, the Allegheny chinkapin, and Castanea dentata, the American chestnut. Morphological evolution of one nut per bur in the genus may have occurred independently on two continents.
栗属（壳斗科）广泛分布于北半球的落叶林中。一个世纪以来，东亚和北美东部植物区系之间的显著相似性以及不同栗种对栗疫病抗性的差异一直吸引着植物学家。为了推断该属的生物地理历史，利用来自叶绿体基因组不同区域的DNA序列数据估计了栗属的系统发育。测序结果支持栗属作为一个单系类群，其中日本栗为基部类群。三个中国栗种形成了一个得到有力支持的姐妹分支，与北美和欧洲分支相对。推测现存栗种有一次独特的向西扩张，栗属起源于东亚，在始新世期间在亚洲内部初步分化，随后在始新世中期发生洲际扩散并在中国种与欧洲/北美种之间产生分化，在始新世晚期欧洲种与北美种之间出现分支。北美和中国内部的分化可能发生在中新世早期或晚期。北美栗种被支持为一个分支，以奥扎克矮栗（C. pumila var. ozarkensis）作为基部谱系，它是包括阿勒格尼矮栗（C. pumila var. pumila）和美洲栗（Castanea dentata）在内的类群的姐妹。该属中每个壳斗一个坚果的形态演化可能在两大洲独立发生。
