Metabolic profiling reveals a functional succession of active fungi during the decay of Mediterranean plant litter

We evaluated the relationship between the potential activity shown by pure fungal isolates (in vitro) and their ecological role in the field. Fungal species frequency and occurrence during trophic succession on a natural resource were studied and used as a tool to gain a better understanding of the metabolic profiles obtained in vitro, thus permitting clarification of the role played by some of the key fungal species involved in the decomposition process within a Mediterranean natural ecosystem. Litter bags containing pure (homogeneous) and mixed leaves of low maquis plant species were incubated for one year in a field experiment. Functional diversity of a representative pool of fungal communities was analysed and compared using a “phenotype microarray” technique. Taking as its basis the screening of metabolic profiles using culturable isolates, this investigation showed that there was a high potentiality of functional redundancy between low, intermediate and high frequency taxa, and potential niche overlap during the different phases that occur during leaf litter decomposition. The early stages of decomposition appeared to be characterized by the presence of rare taxa (“Low” species), with a significantly higher functional potential, especially for sugar compounds. Conversely, the later phases of decomposition appeared to be characterized by species of intermediate frequency, while rare taxa at these stages seem to lose their dominant role. The importance of the different groups of substrates found across the decomposition phases also represented a key factor. For example, redundancy in the utilization of N-related compounds indicated a high potential for overlapping between species, especially in the early phases of the decomposition process, suggesting that the capacity for interspecific competition on some substrates can be considerable, particularly at the start of substrate exploitation.