INTERSPECIFIC COMPETITIVE INTERACTIONS BETWEEN PAIRS OF FUNGAL SPECIES IN NATURAL SUBSTRATES

The role of interspecific competition in fungal communities in natural substrates is poorly understood because fungi do not form easily defi nable populations. A new approach to investigating fungal competition, using natural substrates containing a range of known biomass concentr ations of each of two species, is described. Relative competitive succ ess of each species is assessed over time in terms of propagule produc tion and substrate colonisation by each species. In an agricultural so il Mucor hiemalis usually out-competed Trichoderma harzianum. After 27 days, the success of both species in the mixtures was independent of the initial biomass concentration of either species, although the succ ess of T. harzianum in these mixtures was substantially inhibited rela tive to the T harzianum monocultures. In a forest soil, T polysporum m aintained a competitive advantage over M. hiemalis, and induced M. hie malis to produce propagules rather than mycelia. Coexistence of both s pecies always occurred in both experiments, and in the forest soil exp eriment the two-species mixtures all contained a higher total microbia l biomass than the monocultures of either species by day 47, suggestin g some niche differentiation.