Tree endurance on the Tibetan Plateau marks the world’s highest known tree line of the Last Glacial Maximum

Authors

  • Lars Opgenoorth,

    1. Faculty of Biology, Conservation Biology, University of Marburg, Karl-von-Frisch Strasse 8, 35032 Marburg, Germany
    2. Faculty of Geography, University of Marburg, Deutschhausstrasse 10, 35032 Marburg, Germany
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  • Giovanni G. Vendramin,

    1. Istituto di Genetica Vegetale, Sezione di Firenze, Consiglio Nazionale delle Ricerche, Via Madonna del Piano, 50019 Sesto Fiorentino (FI), Italy
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    • Authors who contributed equally to the work presented in this article.

  • Kangshan Mao,

    1. Key Laboratory of Arid and Grassland Ecology, Institute of Molecular Ecology, Lanzhou University, Lanzhou 730000, China
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    • Authors who contributed equally to the work presented in this article.

  • Georg Miehe,

    1. Faculty of Geography, University of Marburg, Deutschhausstrasse 10, 35032 Marburg, Germany
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  • Sabine Miehe,

    1. Faculty of Geography, University of Marburg, Deutschhausstrasse 10, 35032 Marburg, Germany
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  • Sascha Liepelt,

    1. Faculty of Biology, Conservation Biology, University of Marburg, Karl-von-Frisch Strasse 8, 35032 Marburg, Germany
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  • Jianquan Liu,

    1. Key Laboratory of Arid and Grassland Ecology, Institute of Molecular Ecology, Lanzhou University, Lanzhou 730000, China
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  • Birgit Ziegenhagen

    1. Faculty of Biology, Conservation Biology, University of Marburg, Karl-von-Frisch Strasse 8, 35032 Marburg, Germany
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Author for correspondence:
Lars Opgenoorth
Tel: 04964212822080
Email: Lars.Opgenoorth@staff.uni-marburg.de
Jianquan Liu
Tel: 00869318914305
Email: liujq@nwipb.ac.cn

Summary

  • • Because of heterogeneous topographies, high-mountain areas could harbor a significant pool of cryptic forest refugia (glacial microrefugia unrecognized by palaeodata), which, as a result of poor accessibility, have been largely overlooked. The juniper forests of the southern Tibetan Plateau, with one of the highest tree lines worldwide, are ideal for assessing the potential of high-mountain areas to harbor glacial refugia.
  • • Genetic evidence for Last Glacial Maximum (LGM) endurance of these microrefugia is presented using paternally inherited chloroplast markers. Five-hundred and ninety individuals from 102 populations of the Juniperus tibetica complex were sequenced at three polymorphic chloroplast regions.
  • • Significant interpopulation differentiation and phylogeographic structure were detected (GST = 0.49, NST = 0.72, NST > GST, < 0.01), indicating limited among-population gene flow. Of 62 haplotypes recovered, 40 were restricted to single populations. These private haplotypes and overall degrees of diversity were evenly spread among plateau and edge populations, strongly supporting the existence of LGM microrefugia throughout the present distribution range, partly well above 3500 m.
  • • These results mark the highest LGM tree lines known, illustrating the potential significance of high-mountain areas for glacial refugia. Furthermore, as the close vicinity of orographic rear-edge and leading-edge populations potentially allows gene flow, surviving populations could preserve the complete spectrum of rear-edge and leading-edge adaptations.

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