Overlap in substrate utilisation and spatial exclusion in some microfungi which act as early cellulose colonisers in a Mediterranean environment

A trapping system was set up to isolate culturable cellulolytic fungi at the soil-leaf litter interface in an area of Mediterranean maquis located in southern Italy. Seven cellulolytic taxa were isolated and cultured to represent the pioneers in the primordial phase of cellulose colonisation. The functional diversity of fungal isolates was analysed using a phenotype microarray technique to generate a profile of their functional traits. The extent of the overlap in substrate utilisation by the various species was subsequently determined. Some of the species that acted as key cellulose decomposers are considered globally distributed air-borne contaminants. Most of the cellulolytic species that were isolated during the experiment are also well known for their competitive abilities. Our study showed that at an early stage of cellulose colonisation a few fungal species with potential overlap in the overall metabolic function were able to establish themselves. The species that prevailed at the onset of cellulose colonisation did not co-occur in the field sites. A sort of “founder effect” could be hypothesised for microfungi when colonising sterile cellulose. This would suggest that scale (i.e. the spatial component) exerts a strong influence on the causative mechanisms that link genetic fungal diversity to specific ecosystem functions.