title: Mycorrhizal networks and coexistence in species-rich orchid communities.
abstract: Multispecies assemblages often consist of a complex network of interactions. Describing the architecture of these networks is a first step in understanding the stability and persistence of these species-rich communities. Whereas a large body of research has been devoted to the description of above-ground interactions, much less attention has been paid to below-ground interactions, probably because of difficulties to adequately assess the nature and diversity of interactions occurring below the ground. In this study, we used 454 amplicon pyrosequencing to investigate the architecture of the network between mycorrhizal fungi and 20 orchid species co-occurring in a species-rich Mediterranean grasslands. We found 100 different fungal operational taxonomic units (OTUs) known to be mycorrhizal in orchids, most of which were members related to the genera Ceratobasidium and Tulasnella. The network of interactions was significantly compartmentalized (M = 0.589, P = 0.001), but not significantly nested (N = 0.74, NODF = 10.58; P > 0.05). Relative nestedness was negative (N* = -0.014), also suggesting the existence of isolated groups of interacting species. Compartmentalization is a typical feature of ecological systems showing high interaction intimacy, and may reflect strong specialization between orchids and fungi resulting from physiological, physical or spatial constraints.
authors.affiliation: Department of Biology, Plant Conservation and Population Biology, KU Leuven, B-3001, Leuven, Belgium.
authors.forename: Hans
authors.initials: H
authors.lastname: Jacquemyn
authors.affiliation: Department of Biology, Plant Conservation and Population Biology, KU Leuven, B-3001, Leuven, Belgium.
authors.forename: Rein
authors.initials: R
authors.lastname: Brys
authors.affiliation: Department of Biology, Plant Conservation and Population Biology, KU Leuven, B-3001, Leuven, Belgium.
authors.forename: Michael
authors.initials: M
authors.lastname: Waud
authors.affiliation: Department of Microbial and Molecular Systems (M2S), Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Campus De Nayer, KU Leuven, B-2860, Sint-Katelijne-Waver, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Busschaert
authors.affiliation: Department of Microbial and Molecular Systems (M2S), Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Campus De Nayer, KU Leuven, B-2860, Sint-Katelijne-Waver, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Lievens
mesh_terms: D044822:Biodiversity; D065948:Grassland; D058507:Host Specificity; D007558:Italy; D038821:Mycorrhizae / Q000235:genetics / Q000502:physiology*; D029595:Orchidaceae / Q000382:microbiology*; D010802:Phylogeny
keywords: coexistence; compartmentalization; modularity; mycorrhizal fungi; nestedness; network; orchids