Origins and significance of genetic and epigenetic instability in mycelial systems

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Abstract
Fungal mycelia can alter their organizational pattern in such ways as to produce alternative phenotypes. The latter allow mycelia to explore for, assimilate, conserve, and redistribute resources in spatially and temporally heterogeneous niches. It is suggested that mycelia produce alternative phenotypes by operating as nonlinear (feedback regulated), hydrodynamic systems with indefinitely expandable (indeterminate) boundaries. As such, mycelia can vary the resistances of hyphal envelopes to deformation and passage of molecules, and of hyphal interiors to displacement of contents, in accord with fortuitous local circumstances. Within the mycelial protoplasm are populations of nuclei and mitochondria. If disparate in genetic content or expression, these organelles can form diverse and unstable relationships that both influence and are influenced by metabolic processes affecting the hydraulic resistances of hyphae. Some of these processes may be autocatalytic, involving the generation, association and dissociation of free radicals and reactive oxygen species. Once initiated, such processes are beyond immediate genetic control. Fungal mycelia therefore epitomize the complex interplays between adaptive (genetic) and nonadaptive (organizational) processes that regulate the short term versatility and long term evolutionary divergence of indeterminate systems. Key words: epigenetics, mycelial development, networks, niche, nonlinearity, speciation.