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Plant Systematics and Evolution

, Volume 232, Issue 3–4, pp 213–236 | Cite as

The evolutionary history of Fagus in western Eurasia: Evidence from genes, morphology and the fossil record

  • T. Denk
  • G. Grimm
  • K. Stögerer
  • M. Langer
  • V. Hemleben

Abstract.

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 (Malý) 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.

Key words: Fagus sylvatica L. s.l., western Eurasia, intraspecific differentiation, morphology, ITS1, ITS2, intraindividual variability, cloning techniques. 

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Copyright information

© Springer-Verlag Wien 2002

Authors and Affiliations

  • T. Denk
    • 1
  • G. Grimm
    • 2
  • K. Stögerer
    • 2
  • M. Langer
    • 3
  • V. Hemleben
    • 4
  1. 1.Swedish Museum of Natural History, Department of Palaeobotany, Stockholm, SwedenSE
  2. 2.Institute and Museum of Geology and Palaeontology, Eberhard-Karls-University, Tübingen, GermanyDE
  3. 3.Institute of Palaeontology, Rheinische Friedrich-Wilhelms-University, Bonn, GermanyDE
  4. 4.Centre for Plant Molecular Biology, Institute of Genetics, Eberhard-Karls-University, Tübingen, GermanyDE

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