Mycorrhizal
Networks (pp.1-39) (2015)
Randy Molina,
Thomas R. Horton
Abstract
The establishment of common mycelial networks by mycorrhizal fungi shared
between host plants depends on the ability of neighboring plants to enter into
mycorrhizal associations with compatible fungal species. Such compatibility is
governed by the potential mycorrhiza specificities of the symbionts. Mycorrhiza
specificities exist along a continuum from low specificity (association with
multiple partners) to high specificity (association with one or few partners).
Although the ability of symbionts to form mycorrhizas may be largely governed
by host-fungus gene interactions as influenced by co-evolutionary events,
mycorrhizal associations in natural ecosystems can also be influenced by environmental
factors (e.g. soil) and biological factors (e.g. different neighboring host
species), phenomena referred to as “ecological specificity.” For example, in
natural settings, mycorrhizal fungi often express “host preference” wherein
fungi may be more common on a particular host in mixed-host settings than would
be expected by random species assemblage within the fungal and plant
communities. Mycorrhiza specificity phenomena significantly influence plant
community dynamics, particularly plant succession. Early seral plants can
positively affect the establishment of later-seral plants by maintaining
commonly shared mycorrhizal fungi, and thus affecting the function of common
mycelial networks over time. Such knowledge provides guidance for ecosystem
managers to maintain “legacy” early -seral plants that benefit later-seral
plants via shared mycorrhizal fungus species. Understanding specificity
phenomena is also crucial for predicting the successful migration of plants and
compatible mycorrhizal fungi during climate change. We review mycorrhiza
specificity terminology and types of specificity phenomena, and suggest use of
common terms to provide consistency in addressing this research topic. We also
provide extensive examples from diverse ecosystems on the ability (or
inability) of neighboring plants to develop common mycelial networks.