Identification and characterization of vegetation loss during the last 50,000 years in Beringia

Ongoing climate change causes a global biodiversity loss and species extinction by reducing population size and decreasing genetic diversity. Massive extinction events happened in the past with the Megafauna extinction as the latest example. The Pleistocene-Holocene transition also witnessed the loss of the broadly established steppe-tundra biota, spanning most of Northern Hemisphere during the Pleistocene and supporting Pleistocene megafauna at the time. Understanding past extinction events via the investigation of Quaternary records can strengthen the current methods to forecast the effects of global warming on ecosystems. If loss of other organism groups were proportional to what has been shown for mammals, a large part of the Pleistocene steppe-tundra biota might have gone extinct. However, few example are known. The improved taxonomic resolution and high detectability of sedimentary ancient DNA provide a new tool to explore this. Here, we investigate potential plant taxa loss in the Northern Hemisphere between the late Pleistocene-Holocene transition using sedimentary ancient DNA (sedaDNA) metabarcoding. We summarized data from 500 samples comprising nine lake sediment cores from North-East-Asia and North-America spanning the last 50.000 years. Using patterns of past plant diversity (appearance-disappearance through time), we built communities to detect past taxa non-present in modern databases inferring potential candidates for extinction. Our results suggest that vegetation was resilient until the Pleistocene to Holocene transition and that loss appeared in parallel to the Megafauna extinction. Finally, we characterized this vegetation loss and identified that more specialist taxa contributing less to beta diversity are more sensitive to potential extinction than other taxa. This work holds great potential to reveal new insights into the evolution of the fragile boreal plant communities and the processes leading to extinction of species.