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Reproductive strategy, clonal structure and genetic diversity in populations of the aquatic macrophyte Sparganium emersum in river systems.

Abstract

Many aquatic and riparian plant species are characterized by the ability to reproduce both sexually and asexually. Yet, little is known about how spatial variation in sexual and asexual reproduction affects the genotypic diversity within populations of aquatic and riparian plants. We used six polymorphic microsatellites to examine the genetic diversity within and differentiation among 17 populations (606 individuals) of Sparganium emersum, in two Dutch-German rivers. Our study revealed a striking difference between rivers in the mode of reproduction (sexual vs. asexual) within S. emersum populations. The mode of reproduction was strongly related to locally reigning hydrodynamic conditions. Sexually reproducing populations exhibited a greater number of multilocus genotypes compared to asexual populations. The regional population structure suggested higher levels of gene flow among sexually reproducing populations compared to clonal populations. Gene flow was mainly mediated via hydrochoric dispersal of generative propagules (seeds), impeding genetic differentiation among populations even over river distances up to 50 km. Although evidence for hydrochoric dispersal of vegetative propagules (clonal plant fragments) was found, this mechanism appeared to be relatively less important. Bayesian-based assignment procedures revealed a number of immigrants, originating from outside our study area, suggesting intercatchment plant dispersal, possibly the result of waterfowl-mediated seed dispersal. This study demonstrates how variation in local environmental conditions in river systems, resulting in shifting balances of sexual vs. asexual reproduction within populations, will affect the genotypic diversity within populations. This study furthermore cautions against generalizations about dispersal of riparian plant species in river systems.

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  • Authors

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    Source

    Molecular ecology 16:2 2007 Jan pg 313-25

    MeSH

    Angiosperms
    Bayes Theorem
    Demography
    Environment
    Gene Flow
    Gene Frequency
    Genetic Variation
    Genetics, Population
    Germany
    Microsatellite Repeats
    Netherlands
    Reproduction, Asexual
    Rivers

    Pub Type(s)

    Comparative Study
    Journal Article

    Language

    eng

    PubMed ID

    17217347