title: The dark side of the mycorrhiza.
abstract: Plant association with arbuscular mycorrhizal (AM) fungi is usually regarded as mutualistic. However, this positive effect could disappear if the benefit of the fungal-plant association changes with colonization density. In order to test the conditionality of this interaction, we evaluated plant performance and tolerance to defoliation across five levels of commercial AM fungal inoculum concentrations. Additionally, we evaluated if plant performance and tolerance were similarly affected by a whole soil community collected under a native congener. Along the gradient of inoculation, plant performance exhibited a peak at intermediate inoculum concentration, indicating the presence of an optimum level of AM fungal concentration that maximized AM fungal benefit. Root colonization by fungal hyphae increased linearly across the experimental inoculation gradient. Paralleling root colonization, plant tolerance to defoliation decreased linearly along the inoculum gradient. Plant performance was similar under the whole soil and commercial treatments. Our results show a negative correlation between tolerance to defoliation and AM fungal inoculum concentration, indicating that AM fungi colonization could constrain the evolution of plant tolerance to herbivory.
authors: Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, México Distrito Federal, México.
authors: Etzel
authors: E
authors: Garrido
authors: Alison E
authors: AE
authors: Bennett
authors: Juan
authors: J
authors: Fornoni
authors: Sharon Y
authors: SY
authors: Strauss
mesh_terms: D032302:Datura / Q000254:growth & development* / Q000382:microbiology; D025301:Hyphae / Q000502:physiology; D038821:Mycorrhizae / Q000502:physiology*; D018517:Plant Roots / Q000382:microbiology*; D012988:Soil Microbiology; D013559:Symbiosis