Holocene floristic diversity and richness in northeast Norway revealed by sedimentary ancient DNA (sedaDNA) and pollen

Abstract

We present a Holocene record of floristic diversity and environmental change for the central Varanger Peninsula, Finnmark, based on ancient DNA extracted from the sediments of a small lake (sedaDNA). The record covers the period ca. 10,700 to 3,300 cal. a BP and is complemented by pollen data. Measures of species richness, sample evenness, and beta-diversity were calculated based on sedaDNA sampling intervals and 1000-year time windows. We identified 101 vascular plant and 17 bryophyte taxa, a high proportion (86 %) of which are still growing within the region today. The high species richness (>60 taxa) observed in the early-Holocene, including representatives from all important plant functional groups, shows that modern shrub-tundra communities, and much of their species complement, were in place as early as ca. 10,700 cal. a BP. We infer that post-glacial colonisation of the area occurred prior to the Holocene, during the Younger Dryas stadial or earlier. Abundant DNA of the extra-limital aquatic plant Callitriche hermaphroditica suggests it expanded its range northward between ca. 10,200 and 9,600 cal. a BP, when summers were warmer than present. High values of Pinus DNA occur throughout the record, but we cannot say with certainty if they represent prior local presence; however, pollen influx values >500 grains/cm2/a-1 between ca. 8,000 and 7,300 cal. a BP strongly suggest the presence of pine woodland during this period. As the site lies beyond the modern tree limit of pine, it is likely that this expansion also reflects a response to warmer early-Holocene summers.

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ORCID for Mary Edwards: orcid.org/0000-0002-3490-6682

ORCID for Antony Brown: orcid.org/0000-0002-1990-4654

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