Data from: Mycorrhizal network assembly in a community context: the presence of neighbours matters

1. Understanding the factors and mechanisms driving the structure of
ecological networks is a challenge for community ecologists. Notably, it
remains unclear whether observed interaction patterns between two trophic
groups are a result of (1) preferential partner selection between groups,
or (2) species interactions within groups. 2. We conducted an experiment
in order to disentangle these two drivers, using the plant-mycorrhizal
symbiosis as a model system. We followed mycorrhizal colonization of plant
roots growing either with or without neighbours. This allowed us to assess
the relative importance of interaction within trophic groups (here,
plant-to-plant interactions) on ecological network assembly. 3. Results
showed that plants were not equally affected by the presence of neighbours
and that network nestedness was higher when plants grew without
neighbours. We also found a poor correlation between the centrality (i.e.
standardized number of interactions) of plant species grown in communities
and those grown without neighbours, while the reverse was true for
mycorrhizal fungi. This suggests that the optimum level of specificity or
generalism in mycorrhizal selection is not a fixed plant trait, but a
plastic, context-dependent one. 4. Synthesis. Our results show that
ecological networks are not only shaped by preferential partner selection,
but also by interactions within a given trophic group. This finding should
be considered in future modelling exercises on ecological network
dynamics. Moreover, our nestedness results suggest that in the presence of
multiple host plants, mycorrhizal fungi display preferences for specific
interactions, suggesting that local plant diversity may shape mycorrhizal
fungal community structure.