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Molecular evidence for multiple introductions of garlic mustard (Alliaria petiolata, Brassicaceae) to North America

Authors

  • WALTER DURKA,

    Corresponding author
    1. UFZ Centre for Environmental Research Leipzig-Halle Ltd, Department of Community Ecology, Theodor-Lieser Str. 4, D-06120 Halle, Germany
      Walter Durka, Fax: +49 345 5585 329; E-mail: walter.durka@ufz.de
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  • OLIVER BOSSDORF,

    1. UFZ Centre for Environmental Research Leipzig-Halle Ltd, Department of Community Ecology, Theodor-Lieser Str. 4, D-06120 Halle, Germany
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  • DANIEL PRATI,

    1. UFZ Centre for Environmental Research Leipzig-Halle Ltd, Department of Community Ecology, Theodor-Lieser Str. 4, D-06120 Halle, Germany
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  • HARALD AUGE

    1. UFZ Centre for Environmental Research Leipzig-Halle Ltd, Department of Community Ecology, Theodor-Lieser Str. 4, D-06120 Halle, Germany
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Walter Durka, Fax: +49 345 5585 329; E-mail: walter.durka@ufz.de

Abstract

Invasive species offer excellent model systems for studying rapid evolutionary change. In this context, molecular markers play an important role because they provide information about pathways of introduction, the amount of genetic variation introduced, and the extent to which founder effects and inbreeding after population bottlenecks may have contributed to evolutionary change. Here, we studied microsatellite variation in eight polymorphic loci among and within 27 native and 26 introduced populations of garlic mustard (Alliaria petiolata), a European herb which is a current serious invader in North American deciduous forests. Overall, introduced populations were genetically less diverse. However, considerable variability was present and when compared to the probable source regions, no bottleneck was evident. Observed heterozygosity was very low and resulted in high inbreeding coefficients, which did not differ significantly between native and introduced populations. Thus, selfing seems to be equally dominant in both ranges. Consequently, there was strong population differentiation in the native (FST = 0.704) and the introduced (FST = 0.789) ranges. The high allelic diversity in the introduced range strongly suggests multiple introductions of Alliaria petiolata to North America. Out of six European regions, the British Isles, northern Europe, and central Europe had significantly higher proportions of alleles, which are common to the introduced range, and are therefore the most probable source regions. The genetic diversity established by multiple introductions, and the lack of inbreeding depression in this highly selfing species, may have contributed to the invasion success of Alliaria petiolata.

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