Ecological memory and relocation decisions in fungal mycelial networks: responses to quantity and location of new resources

TLDR

Saprotrophic cord‑forming basidiomycetes form mycelial networks that decompose wood and cycle nutrients, yet their foraging intelligence remains poorly understood. The study examines how the relative sizes of inoculum and bait wood influence Phanerochaete velutina’s decision to stay or migrate. Mycelium was grown from an inoculum across a soil microcosm to a wood bait, then the inoculum was relocated to fresh soil to assess regrowth and directional memory. Regrowth occurred in 67 % of inocula, and a threshold bait size—not inoculum‑to‑bait size ratio—triggered final migration, with stronger regrowth on the side initially facing the bait, indicating directional memory.

Abstract

Abstract Saprotrophic cord-forming basidiomycetes, with their mycelial networks at the soil/litter interface on the forest floor, play a major role in wood decomposition and nutrient cycling/relocation. Many studies have investigated foraging behaviour of their mycelium, but there is little information on their intelligence. Here, we investigate the effects of relative size of inoculum wood and new wood resource (bait) on the decision of a mycelium to remain in, or migrate from, inoculum to bait using Phanerochaete velutina as a model. Experiments allowed mycelium to grow from an inoculum across the surface of a soil microcosm where it encountered a new wood bait. After colonisation of the bait, the original inoculum was moved to a tray of fresh soil to determine whether the fungus was still able to grow out. This also allowed us to test the mycelium’s memory of growth direction. When inocula were transferred to new soil, there was regrowth from 67% of the inocula, and a threshold bait size acted as a cue for the mycelium’s decision to migrate for a final time, rather than a threshold of relative size of inoculum: bait. There was greater regrowth from the side that originally faced the new bait, implying memory of growth direction.