Tracking late-Quaternary extinctions in interior Alaska using megaherbivore bone remains and dung fungal spores

One major challenge in the study of late-Quaternary extinctions (LQEs) is providing better estimates of past megafauna abundance. To show how megaherbivore population size varied before and after the last extinctions in interior Alaska, we use both a database of radiocarbon-dated bone remains (spanning 25-0 ka) and spores of the obligate dung fungus,Sporormiella,recovered from radiocarbon-dated lake-sediment cores (spanning 17-0 ka). Bone fossils show that the last stage of LQEs in the region occurred at about 13 ka ago, but the number of megaherbivore bones remains high into the Holocene.Sporormiellaabundance also remains high into the Holocene and does not decrease with major vegetation changes recorded by arboreal pollen percentages. At two sites, the interpretation ofSporormiellawas enhanced by additional dung fungal spore types (e.g.,Sordaria). In contrast to many sites where the last stage of LQEs is marked by a sharp decline inSporormiellaabundance, in interior Alaska our results indicate the continuance of megaherbivore abundance, albeit with a major taxonomic turnover (includingMammuthusandEquusextinction) from predominantly grazing to browsing dietary guilds. This new and robust evidence implies that regional LQEs were not systematically associated with crashes of overall megaherbivore abundance.