Ectomycorrhizae: Co-evolution, significance, and biogeography

The fungus/plant root association known as a mycorrhizal symbiosis appears to have evolved in the Devonian. Of the two general morphological types of mycorrhizae among plant families, arbuscular mycorrhizae appear earlier in the fossil record and are more widespread than are ectomycorrhizae. The latter type of symbiosis most likely evolved with the vascular plant progenitors of modern Pinaceae in the Jurassic, but also developed with the ancestors of a dozen or so extant Angiosperm families. The significance of the ectomycorrhizal relationship is evident in that the symbionts profit by acquiring resources from their partners that would otherwise be unavailable. In natural environments where ectomycorrhizal communities exist, the symbiosis may be restricted or not depending on the particular plants and fungi Involved. The presence of an obligate specificity of a particular fungus with a particular plant has a profound consequence on biogeographic distribution.