Abstract：
OBJECTIVE: The Labrador Teas (genus Rhododendron, subsection Ledum) are a complex of species widely distributed in the Northern Hemisphere. They occupy cold-resistant plant communities from highlands to forest understory and wetland habitats almost circumboreally and they are especially abundant in Northeast Asia (NE Asia) and northern North America (NN Am), still there are no clear species boundaries in this group. The genetic structure of species of the subsect. Ledum from Eurasia and North America as well as the dispersal history of the group require clarification.
METHODS: Phylogeny and biogeography of the subsect. Ledum of the genus Rhododendron were assessed using phylogenetic trees constructed based on the analysis of variation in chloroplast petB-petD, trnV-ndhC, trnH-psbA, K2R-K707, atpB oligo2 - rbcL oligo5 and nuclear (ITS1) markers of four Eurasian and one American species (65 populations, 408 individuals). The data were evaluated with Maximum Parsimony and Bayesian analysis. Molecular dating and ancestral areas reconstruction were obtained.
RESULTS: Dense sampling revealed widespread presence of shared haplotypes and ribotypes among Ledum populations and species. Two American, three Eurasian and one mixed lineage diversified during the Neogene climate cooling and then rapidly dispersed during the Pleistocene. The ability to accumulate high genetic diversity and to preserve it across distribution ranges and generations prevented Ledum from lineage sorting. As a result, a species complex with a reserve of genetic variability appeared.
CONCLUSIONS: Although no clear phylogenetic inference can be obtained at present, the plastid genealogy is consisted with the nuclear genealogy and demonstrates the processes involved in speciation in the Ledum species complex.
METHODS: Phylogeny and biogeography of the subsect. Ledum of the genus Rhododendron were assessed using phylogenetic trees constructed based on the analysis of variation in chloroplast petB-petD, trnV-ndhC, trnH-psbA, K2R-K707, atpB oligo2 - rbcL oligo5 and nuclear (ITS1) markers of four Eurasian and one American species (65 populations, 408 individuals). The data were evaluated with Maximum Parsimony and Bayesian analysis. Molecular dating and ancestral areas reconstruction were obtained.
RESULTS: Dense sampling revealed widespread presence of shared haplotypes and ribotypes among Ledum populations and species. Two American, three Eurasian and one mixed lineage diversified during the Neogene climate cooling and then rapidly dispersed during the Pleistocene. The ability to accumulate high genetic diversity and to preserve it across distribution ranges and generations prevented Ledum from lineage sorting. As a result, a species complex with a reserve of genetic variability appeared.
CONCLUSIONS: Although no clear phylogenetic inference can be obtained at present, the plastid genealogy is consisted with the nuclear genealogy and demonstrates the processes involved in speciation in the Ledum species complex.
摘要：
目的：拉布拉多茶（杜鹃花属，Ledum小节）是北半球广泛分布的物种复合体。它们占据了从高地到森林林下和湿地栖息地的耐寒植物群落，几乎在周围，它们在东北亚（NEAsia）和北美北部（NNAm）尤其丰富，这个群体仍然没有明确的物种界限。亚种物种的遗传结构。来自欧亚大陆和北美的Ledum以及该小组的散布历史需要澄清。
方法：亚科的系统发育和生物地理学。使用基于叶绿体petB-petD变异分析构建的系统发育树评估了杜鹃花属的叶，trnV-ndhC,trnH-psbA,K2R-K707，atpBolig2-rbcLolig5和四个欧亚物种和一个美洲物种的核（ITS1）标记（65个种群，408个人）。使用最大简约和贝叶斯分析对数据进行评估。获得了分子定年和祖先区域重建。
结果：密集采样揭示了Ledum种群和物种之间广泛存在共有的单倍型和核糖型。两个美国人,在新近纪气候变冷期间，三个欧亚和一个混合谱系多样化，然后在更新世期间迅速分散。积累高遗传多样性并在分布范围和世代之间保持遗传多样性的能力阻止了Ledum进行谱系分类。因此,出现了具有遗传变异性的物种复合体。
结论：尽管目前还没有明确的系统发育推断，质体谱系与核谱系组成，并证明了Ledum物种复合体中物种形成的过程。
方法：亚科的系统发育和生物地理学。使用基于叶绿体petB-petD变异分析构建的系统发育树评估了杜鹃花属的叶，trnV-ndhC,trnH-psbA,K2R-K707，atpBolig2-rbcLolig5和四个欧亚物种和一个美洲物种的核（ITS1）标记（65个种群，408个人）。使用最大简约和贝叶斯分析对数据进行评估。获得了分子定年和祖先区域重建。
结果：密集采样揭示了Ledum种群和物种之间广泛存在共有的单倍型和核糖型。两个美国人,在新近纪气候变冷期间，三个欧亚和一个混合谱系多样化，然后在更新世期间迅速分散。积累高遗传多样性并在分布范围和世代之间保持遗传多样性的能力阻止了Ledum进行谱系分类。因此,出现了具有遗传变异性的物种复合体。
结论：尽管目前还没有明确的系统发育推断，质体谱系与核谱系组成，并证明了Ledum物种复合体中物种形成的过程。
