The evolutionary history of Fagus in western Eurasia:: Evidence from genes, morphology and the fossil record
The evolutionary history of Fagus in western Eurasia:: Evidence from genes, morphology and the fossil record
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DOI：
10.1007/s006060200044
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发表时间：
2002-01-01
影响因子：
1.9
通讯作者：
Hemleben, V
中科院分区：
文献类型：
--
作者：
Denk, T;Grimm, G;Hemleben, V
山毛榉是分布于北方温带森林中数量最多、经济价值最高的阔叶树种之一。欧洲和小亚细亚的现代分类群的数量一直是一个争论的问题，最多有五个物种被确认。为了解决分类和系统发育的关系，我们进行了形态和分子遗传学分析，在欧亚大陆西部类群和古生物学证据进行了评估。为了将我们在欧亚大陆西部种群中的发现置于更广泛的背景下，我们的研究包括了同一个水青冈亚属的东亚和北美物种以及两个水青冈亚属的物种。来自小亚细亚的水青冈种群表现出更高的变异性，这也反映在其核rDNA内部转录间隔区（ITS）序列的遗传变异性。种内遗传变异记录在这里是在冲突与以前的ITS研究在水青冈属。来自欧亚大陆西部的水青冈中存在大量的ITS多态性，沿着观察到的形态特征的倾斜变异表明只存在单一物种，即林水青冈L.，在欧洲和小亚细亚。以前公认的分类群，如F。东方水青冈（Fagus moesiaca（Maly）Czeczott）应视为森林水青冈（Fagus sylvatica）的异名。虽然属于Engleriana亚属的物种在遗传上不同于水青冈亚属的物种，但水青冈亚属内的关系无法明确解决。这可能是一个原因，在渐新世时期的属的范围扩展的早期阶段，在水青冈多样化率低，叶和壳斗/坚果化石的均匀性所示。这可能解释了低的整体ITS分歧和高度的多态性遇到的山毛榉亚属，并指出一个较晚的分化，欧亚大陆西部和东亚物种。在更新世和冰川期后西欧的分裂似乎造成了明显的西-东梯度，在现代的欧亚大陆西部的水青冈，但没有在晚第三纪的祖先Fagus sylvatica。
Fagus (beech) is among the most abundant and economically important genera of broad-leaved trees in northern hemisphere temperate forests. The number of modern taxa present in Europe and Asia Minor has long been a matter of debate and up to five species have been recognised. To resolve taxonomic and phylogenetic relationships we conducted morphological and molecular genetic analyses in western Eurasiatic taxa and evaluated palaeontological evidence. To place our findings from western Eurasiatic populations in a broader context additional East Asiatic and North American species of the same subgenus Fagus as well as two species of the subgenus Engleriana were included in our study.The morphological features exhibited in western Eurasiatic populations of Fagus show a west-east gradient that is characterised by strongly overlapping variability between geographical races, Fagus populations from Asia Minor exhibit an even higher variability that is also reflected in their genetic variability of nuclear rDNA internal transcribed spacer (ITS) sequences. The intraspecific genetic variability recorded here is in conflict with previous ITS studies in Fagus. The high amount of ITS polymorphism within Fagus from western Eurasia along with the clinal variation observed for morphological characters suggest the presence of only a single species, Fagus sylvatica L., in Europe and Asia Minor. Previously recognised taxa such as F. orientalis Lipsky and Fagus moesiaca (Maly) Czeczott should therefore be treated as synonyms of Fagus sylvatica. Although species belonging to the subgenus Engleriana were genetically distinct from species of the subgenus Fagus, relationships within the subgenus Fagus could not be clearly resolved. A reason for this could be the low rate of diversification in Fagus during the early phase of range expansion of the genus in the Oligocene period as indicated by the uniformity of leaf and cupule/nut fossils. This may account for the low overall ITS divergence and the high degree of polymorphism encountered in the subgenus Fagus and points to a late differentiation of western Eurasiatic and eastern Asiatic species. Area disruptions during the Pleistocene and the post-glacial recolonisation of western Europe appear to have caused the west-east gradient that is apparent in modern Fagus of western Eurasia but absent in Late Tertiary ancestors of Fagus sylvatica.