Linking biodiversity to mutualistic networks – woody species and ectomycorrhizal fungi

• Main Author: Ecaterina Fodor
• Format: Article
• Language: English
• Published: ‘Marin Drăcea’ National Research-Development Institute in Forestry 2013-05-01
• Series: Annals of Forest Research
• Subjects: temperate broadleaved mixed forest; ectomycorrhizal fungi; mutualistic bipartite networks; nestedness; modularity; connectance; C-score cluster analysis; non metric multidimensional scaling
• Online Access: http://www.editurasilvica.ro/afr/56/1/fodor.pdf

Mutualistic interactions are currently mapped by bipartite networkswith particular architecture and properties. The mycorrhizae connectthe trees and permit them to share resources, therefore relaxing thecompetition. Ectomycorrhizal macrofungi associated with woody species(Quercus robur, Q. cerris, Q. petraea, Tilia tomentosa, Carpinus betulus, Corylus avellana, and Q. pubescens) growing in a temperate, broadleaved mixed forest, from a hilly area near the city of Cluj–Napoca, central Romania were included in a bipartite mutualistic network. Community structure was investigated using several network metrics, modularity and nestedness algorithms in conjunction with C-score index cluster analysis and nonmetric multidimensional scaling (the Kulczynski similarity was index used as most appropriate metric selected by minimal stress criterion). The results indicate that the network presents high asymmetry (hosts are outnumbered by mycobionts at a great extent), high connectance, low modularity, andhigh nestedness, competition playing a secondary role in community assemblage (non significant difference between simulated and observed Cscore).The nestedness pattern is non-random and is comparable to previouslypublished results for other similar interactions containing plants. Inthe proposed network, woody species function exclusively as generalists. Modularity analysis is a finer tool were identifying species roles than centrality measures, however, the two types of algorithms permit the separation of species according to their roles as for example connectors (generalist species) and ultraperipheral species (specialists). Supergeneralist woody species function as hubs for the diverse ectomycorrhizal community while supergeneralistectomycorrhizal fungi glue the hubs into a coherent aggregate.