Sedimentary ancient DNA shows terrestrial plant richness continuously increased over the Holocene in northern Fennoscandia

Abstract

SummaryIt is crucial to understand how climate warming and other environmental factors affect biodiversity, especially in the rapidly changing northern latitudes.We 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.In 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.We 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.

Ancient sedimentary DNA shows rapid post-glacial colonisation of Iceland followed by relatively stable vegetation until Landnám

“…The TDV cores were sampled using 5 mL sterile disposable syringes as described by Voldstad et al (2020) whereas the NYK core was sampled using clean disposable plastic knives and spatulas as described in Rijal et al (2020). All samples were stored at 4°C until DNA extractions.…”

“…We followed the taxonomy of Wąsowicz (2020). Furthermore, the quality of each sample was assessed following the method described by Rijal et al (2020).…”

“…Furthermore, these records from Iceland exhibit an earlier accumulation compared to an accumulation curve for plant taxa based on sedaDNA analyses of ten lakes in northern Fennoscandia (⅔ before 8000 cal. yr BP, Rijal et al, 2020).…”

“…Studies of contemporary vegetation as well as modelling simulations suggest a legacy of glaciation on patterns of taxonomic richness (Stewart et al, 2016;Svenning et al, 2015), whereas pollen records indicate either Early Holocene species saturation (Giesecke et al, 2019(Giesecke et al, , 2012 or dispersal lags (Felde et al, 2018). Studies of ancient DNA may shed new light on this debate as it better detects taxa and provides a higher taxonomic resolution, thereby providing a stronger method to track past species occurrence (Clarke et al, 2020;Liu et al, 2020;Rijal et al, 2020). A recent study of ancient DNA in northern Fennoscandia suggests severe dispersal lags (Rijal et al, 2020), challenging our view of a very mobile arctic flora.…”

“…Studies of ancient DNA may shed new light on this debate as it better detects taxa and provides a higher taxonomic resolution, thereby providing a stronger method to track past species occurrence (Clarke et al, 2020;Liu et al, 2020;Rijal et al, 2020). A recent study of ancient DNA in northern Fennoscandia suggests severe dispersal lags (Rijal et al, 2020), challenging our view of a very mobile arctic flora.…”