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Distribution, phenology and demography of sympatric sexual and asexual dandelions (Taraxacum officinale s.l.): geographic parthenogenesis on a small scale

Authors

  • MARIJE H. VERDUIJN,

    1. Department of Plant Population Biology, Netherlands Institute of Ecology – Centre for Terrestrial Ecology (NIOO-CTE), PO Box 40, 6666 ZG Heteren, the Netherlands
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  • PETER J. VAN DIJK,

    Corresponding author
    1. Department of Plant Population Biology, Netherlands Institute of Ecology – Centre for Terrestrial Ecology (NIOO-CTE), PO Box 40, 6666 ZG Heteren, the Netherlands
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  • JOS M. M. VAN DAMME

    1. Department of Plant Population Biology, Netherlands Institute of Ecology – Centre for Terrestrial Ecology (NIOO-CTE), PO Box 40, 6666 ZG Heteren, the Netherlands
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E-mail: p.vandijk@nioo.knaw.nl.

Abstract

In many plant and animal species, sexual and asexual forms have different geographical distributions (‘geographic parthenogenesis’). The common dandelion Taraxacum officinale s.l. provides a particularly clear example of differing distributions: diploid sexuals are restricted to southern and central Europe, while triploid asexuals occur across Europe. To get a better understanding of the factors underlying this pattern, we studied the distribution and demography of sexuals and asexuals in a mixed population that was located at the northern distribution limit of the sexuals. In this population three adjacent, contrasting microhabitats were found: a foreland and south and north slopes of a river dike. Comparative analyses of the distribution, phenology and demography indicated that sexuals had a stronger preference for the south slope than did asexuals. We therefore propose that the large-scale geographic parthenogenesis in T. officinale is shaped by an environmental gradient which acts upon the sexuals. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82, 205–218.

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