Nonrandom spatial structuring of orchids in a hybrid zone of three Orchis species

Authors

  • Hans Jacquemyn,

    1. Division of Plant Ecology and Systematics, Biology Department, KU Leuven, Kasteelpark Arenberg 31, B-3001 Heverlee, Belgium
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  • Rein Brys,

    1. Research Institute for Nature and Forest, B-1070 Brussels, Belgium
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  • Olivier Honnay,

    1. Division of Plant Ecology and Systematics, Biology Department, KU Leuven, Kasteelpark Arenberg 31, B-3001 Heverlee, Belgium
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  • Isabel Roldán-Ruiz,

    1. Plant Sciences Unit, Institute for Agricultural and Fisheries Research ILVO, Caritasstraat 21, B-9090 Melle, Belgium
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  • Bart Lievens,

    1. Scientia Terrae Research Institute, B-2860 Sint-Katelijne-Waver, Belgium
    2. Laboratory for Process Microbial Ecology and Bioinspirational Management, Lessius University College, Campus De Nayer, Consortium for Industrial Microbiology and Biotechnology (CIMB), Department of Microbial and Molecular Systems, KU Leuven Association, B-2860 Sint-Katelijne-Waver, Belgium
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  • Thorsten Wiegand

    1. Department of Ecological Modelling, UFZ Helmholtz Centre for Environmental Research, PF 500136, DE-04301 Leipzig, Germany
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Author for correspondence:
Hans Jacquemyn
Tel: +32 16321530
Email: hans.jacquemyn@bio.kuleuven.be

Summary

  • Nonrandom  species–species associations may arise from a range of factors, including localized dispersal, intra- and interspecific interactions and heterogeneous environmental conditions. Because seed germination and establishment in orchids are critically dependent upon the availability of suitable mycorrhizal fungi, species–species associations in orchids may reflect associations with mycorrhizal fungi.
  • To test this hypothesis, we examined spatial association patterns, mycorrhizal associations and germination success in a hybrid zone containing three species of the genus Orchis (Orchis anthropophora, Orchis militaris and Orchis purpurea).
  • Hybridization occurred predominantly between O. purpurea and O. militaris. The spatial distribution patterns of most pure species and hybrids were independent from each other, except that of O. purpurea and its hybrids. The fungal community composition of established individuals differed significantly between pure species, but not between hybrids and O. purpurea. Seed germination experiments using pure seeds showed that the highest number of protocorms were found in regions where adult individuals were most abundant. In the case of hybrid seeds, germination was restricted to areas where the mother plant was most abundant.
  • Overall, these results suggest that the observed nonrandom spatial distribution of both pure and hybrid plants is dependent on the contingencies of the spatial distribution of suitable mycorrhizal fungi.

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