Development of an experimental model to investigate the community dynamics of selected saprotrophic wood decomposer fungi from the frigate unicorn
An experimental microcosm system developed to investigate the community dynamics of two- and three-fungal species interactions is described. The microcosm consists of tessellated nutrient agar tiles allowing the varied prescription of: (1) the number of interacting fungal species; (2) the spatial organisation (patchiness) of the distribution of individuals; and (3) the scale of the interaction arena. The system also allows the quantification of interaction outcome in terms of species occupancy within each tile using a destructive re-isolation based plating technique. The outcome and reproducibility of small-scale, pairwise confrontations were used to predict the behaviour of larger two- and three-species interactions. The influence of experimental factors such as species patch size and spatial distribution on the community dynamics were also investigated. The spatial heterogeneity displayed during large-scale three species tessellations was represented by a novel application of principal component analysis, which showed good intuitive agreement with visual assessment of the interaction outcome patterns. The development of a non-destructive method, based on green fluorescent protein labeling of one of the organisms studied, to continuously monitor the development of the interactions is also described. Results indicated that for two species interactions of equal patch size the final outcomes of the large-scale tessellations could be extrapolated from the behaviour of relevant small-scale binary confrontations. However, further investigation revealed that species patch size influenced the temporal dynamics of the system. It was shown that larger patch sizes of species increased the time taken for one species to replace the other. Results also showed that extrapolation of the behaviour of large-scale three species confrontations were not possible from combative hierarchy information derived from the outcome of binary tile confrontations. The outcomes of the three species interactions were shown to be neither random nor fully deterministic and that a degree of stochasticity was displayed in outcome for all tessellations. These findings suggest that the initial spatial distribution of species influence outcome and reproducibility of the interactions. The model therefore demonstrates the complex and coordinated behaviour of fungal mycelia on fungal community development. The work to develop a non-destructive analysis system for the study of fungal interactions was unsuccessful. The work attempted to introduce the gene for green fluorescent protein into the genome of one of the study organisms, C. marmorata, via genetic transformation. Although, the introduction and expression o f exogenous genetic material into the genome of C. marmorata was not successful, it was possible to isolate protoplasts from this species. This is the first known report of this for this species.
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