Secreted enzymatic activities of ectomycorrhizal fungi as a case study of functional diversity and functional redundancy

Introduction Many studies deal with taxonomic diversity (TD) or estimation of functional traits of ectomycorrhizal communities. However, to our knowledge, none of them has ever tried to calculate the functional diversity (FD) of those communities, which is of critical importance for the diversity and reliability of nutrient supply to the tree. Objectives Here, we propose to evaluate the functional diversity of ECM communities in their potential ability to mobilise nutrients from organic matter, in two different forest stands. Results Results show that in both forest stands: TD is strongly correlated with FD. ECM species are functionally redundant within the communities for their abilities to secrete organic matter degrading enzymes. The functional traits (enzymatic activities) of the studied ectomycorrhizal communities are not related within genera, nor within families or phylogenetically related groups of taxa. Some species show a wide phenotypic plasticity for their enzymatic profiles. Conclusion This study provides the first evidence of functional redundancy in ectomycorrhizal communities. More studies are now needed to evaluate the robustness of these results at wider ecosystem scales and using other relevant functional traits.