Continuity of eastern Beringian megafauna phylogenetic diversity following deposition of the Late Pleistocene Dawson tephra

Volcanic eruptions can deposit ash, or tephra, across the landscape hundreds to thousands of kilometers from the source volcano. The ecological and genetic effects of ancient ashfall events are only known sparsely from the geological record and from modern genomic studies. About 29,000 years ago, a volcanic eruption in the Aleutian archipelago deposited ash across the eastern Beringian mammoth steppe. The resulting Dawson tephra is visible in loess deposits in interior Alaska and Yukon, with thicknesses ranging from 5 to 80 cm at a distance of 1,700 km from its source. To explore the impact of this ashfall event on ecosystem dynamics, we used sedimentary ancient DNA (sedaDNA) approaches to isolate population and community level genomic data from several exposures of Dawson tephra in the Klondike region of Yukon, Canada. We found no significant changes to species assemblages associated with the ashfall event, and no significant change in megafauna phylogenetic diversity after the ashfall. Our results suggest that the Beringian mammoth steppe ecosystem was resilient to ecological disturbance and reinforce the value of sedaDNA to investigate past environmental dynamics.