More AMF colonization leads to more P uptake, bigger milkweeds, and faster growing caterpillars

A recent article in the Journal of Ecology entitled, "Mycorrhizal abundance affects the expression of plant resistance traits and herbivore performance," addressed knowledge gaps in how variation in the amount of arbuscular mycorrhizal fungi (AMF) present in the soil affects colonization of plant roots, nutrient uptake, and subsequent effects on plant performance and trophic interactions with herbivores. In the first experiment, soil abundance of AM fungi was manipulated by changing the amount of inoculum to be from zero to normal soil levels and common milkweed was planted in that soil. More fungi lead to greater root colonization and formation of mycorrhizae that improved phosphorus (P) acquisition and milkweed growth. In the second experiment, a smaller number of AM fungi soil levels were used and caterpillar eggs of the Monarch butterfly were allowed to hatch on growing plants and their biomass accumulation was measured after 5 days of the caterpillars consuming milkweed leaves. Increasing soil abundance of AM fungi inoculum lead to greater plant growth with more nutrient rich leaves and reduced herbivore resistance that benefited the growth of caterpillars. The results are summarized in the following figure.

This article demonstrated that increasing abundance of AM fungi in the soil increased root colonization and formation of mycorrhizae. Increased amounts of mycorrhizae increased milkweed phosphorus (P) uptake. Caterpillars of the Monarch butterfly benefitted from the nutrient rich leaves and grew faster. (figured created by RBN based on data from the cited article)