J Plant Ecol ›› 2016, Vol. 9 ›› Issue (1): 87-99.doi: 10.1093/jpe/rtv035

• Research Articles • Previous Articles     Next Articles

Mixed reproduction strategy and polyploidy facilitate dominance of Kobresia pygmaea on the Tibetan Plateau

Elke Seeber1,2,6,*, Georg Miehe3, Isabell Hensen2,4, Yongping Yang5, and Karsten Wesche1,4   

  1. 1 Botany Department, Senckenberg Museum of Natural History Görlitz, PO Box 300 154, D-02806 Görlitz, Germany; 2 Department of Geobotany and Botanical Garden, University Halle-Wittenberg, Am Kirchtor 1, D-06108 Halle (Saale), Germany; 3 Department of Geography, University Marburg, Deutschhausstraße 10, D-35032 Marburg, Germany; 4 German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, D-04103 Leipzig, Germany; 5 Kunming Institute of Botany, Chinese Academy of Sciences, Heilongtan 650204, Kunming, China; 6 Present address: Department of Geography, University Marburg, Deutschhausstraße 10, D-35032 Marburg, Germany
  • Received:2014-09-02 Accepted:2015-03-31 Online:2015-04-19 Published:2016-01-27
  • Contact: Seeber, Elke E-mail:eseeber.botany@gmail.com

Abstract: Aims The sedge Kobresia pygmaea is the dominant species of high-altitude pastures in Tibet, and it is the most important source of forage in animal husbandry. We present the first comprehensive reproduction study for this perennial key species that adopts a molecular approach and tests how sexual and vegetative reproduction, as well as ploidy, relate to survival and dominance under harsh conditions.
Methods We assessed inflorescence numbers of K. pygmaea across two Tibetan alpine pastures with differing grazing regimes. Germination was tested in untreated diaspores and then following mechanical and chemical scarification. In a 4-year experiment, we assessed diaspore viability and seed bank formation. Using eight microsatellite markers, we recorded multilocus genotypes in hierarchical grids and measured their ploidy using flow cytometry. Adjusted analysis of variance models were used to analyse data on sexual reproduction, while the complement of the Simpson index and the Shannon diversity index were used to characterize the spatial distribution of multilocus genotypes and clonal richness.
Important findings Inflorescence production was high and differed significantly between years (2010: 617±460 SD; 2012: 2015±1213 SD) but not between grazing regimes. Diaspore viability was high (94%) and gradually decreased after 3 and 4 years of storage in the soil. Diaspores not exposed to further scarification failed to germinate, while mechanical and chemical (H 2 SO 4) scarification increased germination to 9 and 44%, respectively. Clonal diversity was high, although in situ germination was rarely observed. Multilocus genotypes intersected and covered a mean area of 0.74 m 2. Most individuals were found to be tetraploid, with only 0.8% of all ramets being triploid. We conclude that K. pygmaea survives on the Tibetan Plateau by employing a mixed reproduction strategy involving both sexual and clonal propagation. The species' adaptability and dominance is further facilitated by its polyploidy. As pasture restoration using diaspores would be difficult, existing Kobresia pasture should be managed more sustainably.

Key words: alpine rangelands, clonal diversity, flow cytometry, grazing, microsatellite analyses

摘要:
Aims The sedge Kobresia pygmaea is the dominant species of high-altitude pastures in Tibet, and it is the most important source of forage in animal husbandry. We present the first comprehensive reproduction study for this perennial key species that adopts a molecular approach and tests how sexual and vegetative reproduction, as well as ploidy, relate to survival and dominance under harsh conditions.
Methods We assessed inflorescence numbers of K. pygmaea across two Tibetan alpine pastures with differing grazing regimes. Germination was tested in untreated diaspores and then following mechanical and chemical scarification. In a 4-year experiment, we assessed diaspore viability and seed bank formation. Using eight microsatellite markers, we recorded multilocus genotypes in hierarchical grids and measured their ploidy using flow cytometry. Adjusted analysis of variance models were used to analyse data on sexual reproduction, while the complement of the Simpson index and the Shannon diversity index were used to characterize the spatial distribution of multilocus genotypes and clonal richness.
Important findings Inflorescence production was high and differed significantly between years (2010: 617±460 SD; 2012: 2015±1213 SD) but not between grazing regimes. Diaspore viability was high (94%) and gradually decreased after 3 and 4 years of storage in the soil. Diaspores not exposed to further scarification failed to germinate, while mechanical and chemical (H 2 SO 4) scarification increased germination to 9 and 44%, respectively. Clonal diversity was high, although in situ germination was rarely observed. Multilocus genotypes intersected and covered a mean area of 0.74 m 2. Most individuals were found to be tetraploid, with only 0.8% of all ramets being triploid. We conclude that K. pygmaea survives on the Tibetan Plateau by employing a mixed reproduction strategy involving both sexual and clonal propagation. The species' adaptability and dominance is further facilitated by its polyploidy. As pasture restoration using diaspores would be difficult, existing Kobresia pasture should be managed more sustainably.

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