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River dynamics shape clonal diversity and genetic structure of an Amazonian understorey herb

Authors

  • Matthias Schleuning,

    Corresponding author
    1. Plant Ecology, Department of Biology, University of Marburg, Karl-von-Frisch Str. 8, 35043 Marburg, Germany
      Correspondence author. Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, 60325 Frankfurt (Main), Germany. E-mail: matthias.schleuning@senckenberg.de
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  • Thomas Becker,

    1. Plant Ecology, Department of Biology, University of Marburg, Karl-von-Frisch Str. 8, 35043 Marburg, Germany
    2. Department of Ecology and Ecosystem Research, Albrecht von Haller Institute for Plant Sciences, University of Goettingen, Untere Karspuele 2, 37073 Goettingen, Germany
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  • Giovana P. Vadillo,

    1. Faculty of Biological Sciences, National University of San Marcos (UNMSM), Venezuela Av. 34, Lima 1, Peru
    2. Department of Community Ecology (BZF), UFZ-Helmholtz Centre for Environmental Research, Theodor-Lieser Str. 4, 06120 Halle, Saale, Germany
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  • Thomas Hahn,

    1. Department of Community Ecology (BZF), UFZ-Helmholtz Centre for Environmental Research, Theodor-Lieser Str. 4, 06120 Halle, Saale, Germany
    2. ITES Ecosystem Management, ETH Zurich, Universitaetsstr. 16, 8092 Zurich, Switzerland
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  • Diethart Matthies,

    1. Plant Ecology, Department of Biology, University of Marburg, Karl-von-Frisch Str. 8, 35043 Marburg, Germany
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  • Walter Durka

    1. Department of Community Ecology (BZF), UFZ-Helmholtz Centre for Environmental Research, Theodor-Lieser Str. 4, 06120 Halle, Saale, Germany
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Correspondence author. Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, 60325 Frankfurt (Main), Germany. E-mail: matthias.schleuning@senckenberg.de

Summary

1. Clonal herbs are an important feature of the understorey of Amazonian forests. However, little is known about the environmental drivers determining the population genetics of these herbs and about the spatial scale of gene flow.

2. With amplified fragment length polymorphism markers, we analysed the clonal diversity and genetic structure of a clonal Amazonian herb (Heliconia metallica) in south-eastern Peru at two spatial scales. First, we sampled leaves in 24 patches differing in flooding frequency and canopy openness in 2 km2 of a floodplain forest, and second in 21 riverine populations from the Andean foothills to the Amazon lowlands along a 550-km stretch of river.

3. At the small spatial scale in the floodplain forest, the clonal diversity of H. metallica was higher at flooded than at non-flooded sites, but clonal diversity did not increase with canopy openness.

4. At the large spatial scale, clonal diversity was very low in riverine populations at up- and downriver sites, suggesting that seedling recruitment was higher at mid-altitudes where the flooding intensity is intermediate. Genetic diversity of riverine populations monotonously increased downriver, indicating unidirectional gene flow mediated by hydrochory.

5. Genetic differentiation among riverine populations was very low (FST = 0.06) and followed an isolation-by-distance pattern, indicating a stepping-stone type of gene flow by seeds. Despite the much smaller spatial scale, genetic differentiation among patches in the floodplain forest was higher (FST = 0.16), due to spatially restricted gene flow in the forest understorey.

6.Synthesis. The genetic structure of H. metallica is the result of seedling recruitment being largely limited to flooded sites and of hydrochoric seed dispersal between populations growing on riverbanks. We conclude that river dynamics are the major determinant of the genetic structure of Amazonian plants and that largely undisturbed river systems, such as the Amazon, provide a crucial vector for gene flow, even at large spatial scales.

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