Lake site information.

Overview map of the North Atlantic. Lake sedaDNA sites with vascular plant histories since local deglaciation shown in yellow (see Table 1 for site information). The extent of the Last Glacial Maximum (LGM) ice sheets is delineated in blue (Batchelor et al., 2019).

Comparison of paleoclimate and lake sedaDNA records from Iceland. A) Presence/absence sedaDNA record from Stóra Viðarvatn (green) and Torfdalsvatn (red) for Betulaceae and Salicaceae, where light gray markers denote that no taxa was detected. For Stóra Viðarvatn sedaDNA, the bubble size is proportional to the number of PCR replicates, and vertical dark gray lines denote the timing of each lake’s deglaciation. B) Biomarker-proxy record of sea ice from the North Iceland Shelf (inverted), where greater concentrations of IP25 correspond to more sea ice (Xiao et al., 2017). C) Diatom-based SST record from the North Iceland Shelf (Sha et al., 2022).

Simplified paleovegetation records from Torfdalsvatn for two taxa: Salix spp. and Betula spp. Shown are pollen counts (bold red lines), where shaded regions indicate values above the mean (Rundgren, 1995), first occurrence of taxa macrofossils (black leaves, Rundgren, 1998), and DNA presence (light red bars, Alsos et al., 2021).

Simplified paleovegetation records from northeast Iceland for two taxa: Salix spp., and Betula spp. Shown are Ytra-Áland pollen counts (bold green lines), where shaded regions indicate values above the mean (Karlsdóttir et al., 2014) and DNA presence (light green bars) from Stóra Viðarvatn (this study).

Timing of postglacial Salicaceae and Betulaceae colonization in the circum North Atlantic at 10 locations (see site numbers in Figure 1 and Table 1). A) GISP2 δ18O reflective of regional North Atlantic temperature variability (Seierstad et al., 2014), and B) lake sedaDNA records of vascular plants, where the brown boxes reflect the extent of sedimentary record and the red/blue circles denote the first appearance of Salicaceae/Betulaceae (Epp et al., 2015; Crump et al., 2019; Alsos et al., 2016, 2021, 2022; Volstad et al., 2020; Rijal et al., 2021; ter Schure et al., 2021; this study). Light red and blue circles denote the presence of a low number of taxa reads, which we conservatively do not interpret to reflect genuine presence (e.g., Epp et al., 2015). Grey circles denote the minimum timing of local deglaciation inferred from basal core ages, and in the case of Baffin Island, cosmogenic radionuclide dating of the lake’s impounding moraine (Crump et al., 2019).

Colonization time after deglaciation for Salicaceae (red) and Betulaceae (blue) for all circum North Atlantic sites (see site numbers in Figure 1 and Table 1). Each point’s color is scaled to the distance the lake is from the closest possible source outside the LGM ice sheet margins.

Primer Sequences used in metabarcoding and qPCR experiments.