Interspecific fungal interactions in spatially heterogeneous systems

Abstract

The community dynamics of two‐ and three‐fungal species interactions derived for a tessellated agar model system are described. The microcosm allows for the varied prescription of: (1) the number of fungal species interacting; (2) the spatial configuration (patchiness) of the distribution of individuals; (3) the magnitude of scale of spatial occupation by different fungal individuals; and (4) the operation of antagonistic mechanisms based on contact or longer range diffusible components. Stepwise logistic regressions for two‐species interactions are used to inform the design of the multi‐species interaction tessellations. The model prescribes and investigates complex parameters, such as spatiotemporal heterogeneity and microcosm scale (e.g. population patchiness and crossing times). Data are quantified as proportion, interface class and state transition class of viable fungal species. Spatiotemporal heterogeneity is represented using a novel application of principal component analysis which shows good intuitive agreement with visual assessment of the interaction outcome patterns, and allows effective comparison of the data as a whole. The model demonstrates the influence of the complex and coordinated behaviour of fungal mycelia on community development: interaction outcome of three‐species interactions cannot be directly extrapolated from the relevant binary component interactions; interaction outcomes of the multi‐species tessellations appears to be neither random nor fully deterministic; a degree of stochasticity is apparent in all tessellation arrangements; the smaller scale tessellations produce more consistent interaction outcome results, probably because experimental scale affects the duration of transient behaviour; and different initial spatial configurations of inoculum (irrespective of inoculum quantity or proportion) influence community development and reproducibility.

Interspecific combative interactions between wood-decaying basidiomycetes

“…Not surprisingly, in view of the difficulties of observation in wood, interactions have been most commonly studied in agar culture in the laboratory (e.g. [6,7,15,16,19,25–30]). While such an approach can provide valuable information, interpretation of outcomes and extrapolation to the field must be made with caution, since results of interactions in agar culture and natural substrata are not necessarily the same (e.g.…”

“…When both were extending from 4 week wood blocks the outcome was deadlock. Initial spatial configuration of inoculum in complex tesselations of more than two species considerably influences community development regardless of inoculum quantity or proportion [30].…”

“…Again this is a non‐additive situation where results of pairwise interactions cannot successfully predict that of a three‐ or higher‐way interaction. For example, in agar Poria placenta replaced Coniophora marmorata, C. marmorata replaced the imperfect fungus Paecilomyces variotii , while P. placenta deadlocked with P. variotii [30]. Extrapolation to three species interactions might suggest that P. variotii would be replaced by C. marmorata , which would in turn replace P. placenta .…”

“…Extrapolation to three species interactions might suggest that P. variotii would be replaced by C. marmorata , which would in turn replace P. placenta . However, tessellations of three species resulted in variable outcomes [30]. In another example, outcome of interactions between pairs of wood decay basidiomycetes in agar culture often differed in the presence of diffusible metabolites of the non‐wood decay fungus Trichoderma harzianum [33].…”

Biomass recycling and the origin of phenotype in fungal mycelia

“…A mycelium, or fungal colony, has no characteristic scale above that of an individual hypha (the basic unit of the mycelium) and can potentially persist indefinitely, reproducing when environmental circumstances are favourable. The connected nature of the mycelial network means that local behaviour can, and is, affected by conditions in remote parts of the colony via mechanisms including translocation (White et al 1998;Bown et al 1999;Olsson 1999). Therefore, the behaviour of the colony is dependent on the interaction between genotype and a complex spatial convolution of environmental conditions across the whole mycelium.…”