Holocene plant diversity revealed by ancient DNA from 10 lakes in northern Fennoscandia

O_LIIt is crucial to understand how climate warming and other environmental factors affect biodiversity, especially in the rapidly changing northern latitudes. C_LIO_LIWe use sedimentary ancient DNA (sedaDNA) metabarcoding to estimate taxonomic richness, and local and regional species pools of terrestrial plants for 10 lakes in northern Fennoscandia over the Holocene. C_LIO_LIIn total, 288 taxa were found in the 316 samples analysed, with local species pools of 89-200 and mean taxonomic richness of 21-65 per catchment. Quality control showed that sedaDNA is a reliable estimate of richness. Local and regional species pools showed a steep increase in the Early Holocene, when the highest rate of warming took place, and continued to increase through the Middle and into the Late Holocene, although temperature decreased over these periods. Only the regional species pool levels off during the last two millennia. Richness and local species pools were always higher in catchments with higher bedrock nutrient availability. C_LIO_LIWe find sedaDNA to be a good proxy for diversity, opening avenues to detect patterns hereto unknown, and we provide a robust methodological approach to its application. Our findings suggest we can expect time lags and environmental factors to affect species richness also of the following global warming. C_LI