The Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
Am J Bot. 2013 Apr;100(4):801-14. doi: 10.3732/ajb.1200250. Epub 2013 Mar 28.
The genetic structure of North American herbaceous Smilax, a clade of closely related understory herbs that has a wide and disjunct distribution, was investigated to test the hypothesis of whether a northern refugium in the upper Midwest may have existed for these plants during the last glaciation.
We analyzed 33 populations sampled from California and throughout the eastern United States using AFLP and chloroplast DNA sequence data.
Individuals of S. jamesii from northern California formed a clade sister to the eastern North American species, and they likely diverged from each other during the Pleistocene. Among the eastern species, two lineages were found on opposite sides of the Appalachian Mountains. The populations near the "Driftless Area" contained most of the chlorotypes found in the Midwest, including a unique one endemic to this area, and the AFLP data indicated that one population from this area has the highest frequency-down-weighted-marker value.
This study, and others that have focused on mammals, amphibians, and woody plants, provides further evidence for the debate over whether the upper Midwest's "Driftless Area" may have hosted a biologically diverse northern glacial refugium. Herbaceous species of Smilax from eastern North American exhibit an Appalachian discontinuity. They appear to have persisted in multiple refugia both east and west of the Appalachians, with several populations persisting in situ through the Last Glacial Maximum (LGM). We suggest that they experienced localized expansion after the LGM, possibly followed by subsequent contact between the Midwest and the East Coastal lineages.
本研究旨在调查北美的草本菝葜（Smilax）的遗传结构，该种为具有广泛而分散分布的密切相关林下草本植物的一个分支。这是为了检验一个假说，即在末次冰期期间，中西部地区是否存在一个北方避难所。
我们使用 AFLP 和叶绿体 DNA 序列数据分析了来自加利福尼亚州和美国东部的 33 个种群。
来自加利福尼亚州北部的菝葜种个体形成了一个与北美东部物种的姐妹群，它们可能在更新世期间彼此分化。在东部物种中，在阿巴拉契亚山脉的两侧发现了两个谱系。“无溪流区”附近的种群包含了在中西部发现的大部分叶绿体类型，包括一种特有于该地区的独特类型，并且 AFLP 数据表明，该地区的一个种群具有最高的频率加权标记值。
这项研究以及其他针对哺乳动物、两栖动物和木本植物的研究为关于中西部地区的“无溪流区”是否可能是一个具有丰富生物多样性的北方冰川避难所的争论提供了进一步的证据。来自北美东部的草本菝葜物种表现出阿巴拉契亚山脉的不连续性。它们似乎在阿巴拉契亚山脉的东西两侧都存在多个避难所，并在末次冰期最大值（LGM）期间有几个种群在原地生存。我们认为，它们在 LGM 之后经历了局部扩张，随后可能与中西部和东海岸谱系之间发生了接触。
