On the origin of feces: Fungal diversity, distribution, and conservation implications from feces of small mammals

Abstract

Fungi are highly diverse, but only a small fraction of the total estimated species have been characterized. Often, the extent of diversity and distribution of fungal communities is difficult or near impossible to assess due to the fact that many fungi are cryptic and persist predominantly hidden within substrates such as soil or plant material. This is particularly true for hypogeous sporocarps, such as truffles and false truffles, which are extremely difficult to survey in a systematic manner. However, hypogeous fungi have evolved traits that make them highly attractive to animals, such as small mammals, which ingest and disperse fungal spores through defecation. Here, samples of feces from 138 small mammal museum vouchers collected in the western United States were assessed for total fungal diversity using a dual-index metabarcoding approach. Our findings exhibit many identifications within the mushroom-forming fungi (Agaricomycetidae), with 65 of the 138 samples containing sequences belonging to several species of the false truffle-forming genus Rhizopogon. Metadata for each collection, such as geospatial coordinates, can be used as a proxy for the presence or absence of Rhizopogon species identified in their feces. Utilizing these proxy data from only a few years of sampling, these records quadrupled the rate of observations of Rhizopogon made over the past 100 years, including some species that have only been recorded once previously. This substantial increase in datapoints has implications for how fungal distributions are interpreted, with direct impact on standard assessment tools for fungal conservation.