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Evolution of ectomycorrhizal symbioses.
Ectomycorrhizal fungi represent diverse lineages of homobasidiomycetes
Hibbett et al. performed phylogenetic analyses of nuclear and mitochondrial rDNA sequences in diverse homobasidiomycetes
Transitions between mycorrhizal and free-living lifestyles were “mapped” onto the phylogeny using parsimony and maximum likelihood methods
Results suggest that there have been at least six origins of mycorrhizal symbioses in homobasidiomycetes, as well as about four reversals to the free-living condition.
These findings contradict the view that “mutualisms” are evolutionarily stable.
Reference:
Hibbett, D. S., L.-B. Gilbert, and M. J. Donoghue. 2000. Evolutionary instability of ectomycorrhizal symbioses in homobasidiomycetes. Nature 407: 506-508.