Sedimentary ancient DNA from Lake Skartjørna, Svalbard: Assessing the resilience of arctic flora to Holocene climate change

Abstract

Reconstructing past vegetation and species diversity from arctic lake sediments can be challenging because of low pollen and plant macrofossil concentrations. Information may be enhanced by metabarcoding of sedimentary ancient DNA ( sedaDNA). We developed a Holocene record from Lake Skartjørna, Svalbard, using sedaDNA, plant macrofossils and sediment properties, and compared it with published records. All but two genera of vascular plants identified as macrofossils in this or a previous study were identified with sedaDNA. Six additional vascular taxa were found, plus two algal and 12 bryophyte taxa, by sedaDNA analysis, which also detected more species per sample than macrofossil analysis. A shift from Salix polaris-dominated vegetation, with Koenigia islandica, Ranunculaceae and the relatively thermophilic species Arabis alpina and Betula, to Dryas octopetala-dominated vegetation ~6600–5500 cal. BP suggests a transition from moist conditions 1–2°C warmer than today to colder/drier conditions. This coincides with a decrease in runoff, inferred from core lithology, and an independent record of declining lacustrine productivity. This mid-Holocene change in terrestrial vegetation is broadly coincident with changes in records from marine sediments off the west coast of Svalbard. Over the Holocene sedaDNA records little floristic change, and it clearly shows species persisted near the lake during time intervals when they are not detected as macrofossils. The flora has shown resilience in the presence of a changing climate, and, if future warming is limited to 2°C or less, we might expect only minor floristic changes in this region. However, the Holocene record provides no analogues for greater warming.

Holocene vegetation change in northernmost Fennoscandia and the impact on prehistoric foragers 12 000–2000 cal. a BP – A review

“…; Alsos et al . ). In addition, one may have to look to the marine environmental change (Jørgensen ).…”

Lake sedimentary DNA accurately records 20th Century introductions of exotic conifers in Scotland

“…Pollen of anemophilous taxa, such as conifer and broadleaved trees, as well as most graminoids, has a large source area and potentially it could to a great extent represent regional vegetation (see Sjögren et al ., , , ). DNA primarily represents local vegetation (near the lakes and within their hydrological catchments; Alsos et al ., ). Pollen values are affected by species‐specific pollen productivity and dispersal properties (e.g.…”

“…Resulting barcodes were then assigned to taxa using the ecotag program (Yoccoz et al ., ) with both regional (Sønstebø et al ., ; Willerslev et al ., ) and global (EMBL release r117) reference libraries, as was done by Alsos et al . (). After data filtering, 11 171 750 reads of 17 145 unique sequences assigned to the 25 sediment samples were retained.…”

Ancient plant DNA in lake sediments

“…These studies (see also Table ) show how DNA can often identify more species and at higher taxonomic resolution than those identified by pollen and macrofossil analyses, thus providing important ecological and climatic information on the investigated sites that is otherwise difficult or impossible to infer (Sønstebø et al ., ; Parducci et al ., ). DNA studies generally identify more herbs (Willerslev et al ., ; Alsos et al ., ) and have greater taxonomic resolution for grasses, thus providing better information on local biodiversity and for the reconstruction of palaeoenvironments. The latter is an advantage compared with pollen, especially at high latitudes/altitudes where local pollen productivity is low and long‐distance pollen dispersal is more common.…”