Climate variability shapes the mutualistic interaction between truffle‐like ectomycorrhizal (ECM) fungi and a mycophagous mammal

The mutualistic interaction between truffle‐like ectomycorrhizal (ECM) fungi and mycophagous mammals is fundamental to forest health, supporting fungal dispersal, soil structure, nutrient cycling, and plant community dynamics worldwide. However, climate change may disrupt this mutualism in unprecedented ways by altering truffle‐like ECM sporing body production and mycophagous mammal diets, with consequences for fungal spore dispersal and ECM host plant health. As one of the most specialised mycophagous mammals in the world, the endangered marsupial long‐footed potoroo Potorous longipes provides a powerful model system to investigate these risks. Using a unique 23‐year collection of long‐footed potoroo scats from south‐eastern Australia, we quantified the diversity and composition of truffle‐like ECM fungi in their diet and assessed how it was shaped by intra‐ and inter‐annual shifts in temperature and precipitation. ITS2 metabarcoding of scats revealed a high richness of truffle‐like ECM fungi in long‐footed potoroo scats, with a total of 38 taxa from 14 genera. The richness of truffle‐like ECM fungi consumed by long‐footed potoroos was negatively correlated with higher minimum temperatures of the previous quarter and 12 months, and was highest in spring. Seasonality, precipitation, minimum temperature and aridity were the best predictors of truffle‐like ECM fungal community composition in long‐footed potoroo scats. We found that five truffle‐like ECM fungal genera – Mesophellia , Hysterangium, Arcangeliella, Thaxterogaster and Austrogautieria – were associated with specific climate conditions related to temperature and precipitation, providing novel insights into their phenology and dispersal. Our findings suggest that mycophagous mammals may consume far less diverse fungal diets in a warmer and drier future, with a greater reliance on truffle‐like ECM fungal genera associated with these conditions such as Mesophellia . These results highlight the sensitivity of this mutualism to climate variability and change, with implications for long‐footed potoroo nutrition, dispersal of truffle‐like ECM fungi, and ecosystem functioning.