Understanding the Coprophilous fungus Sporormiella as a proxy for megaherbivores

Abstract

In many studies, the presence of the coprophilous fungus Sporormiella in Quaternary sediments has been interpreted as evidence of past megaherbivore activity. Despite its use as an ecological proxy, little is known about the taxonomy and life history of Sporormiella, and the taphonomic processes that lead to its preservation in lake sediments. This information underlies its utility to interpret past herbivore presence and abundance. Present-day bison (Bison bison) dung from Yellowstone National Park was examined to explore the production, dispersal, transportation, deposition, and preservation of Sporormiella there. While Sporormiella was found in dung samples, sediments from two lakes frequently visited by bison failed to yield Sporormiella spores. Laboratory preparation techniques were modified to increase the likelihood of Sporormiella spore survival, yet no spores were identified with the new treatment. Although the occurrence of spores in lake-sediment samples may indicate herbivore presence, our study suggests that spore absence does not necessarily indicate an absence of herbivores. We attribute the absence of spores in sediments to local climatic and seasonal factors that may affect production and transport in the watershed, sedimentary processes that may destroy spores after deposition, and harsh laboratory processing techniques that may damage or destroy spores. More research remains to be done to evaluate the importance of these factors before using Sporormiella as a reliable proxy of herbivore activity.