Potential palaeoflora of Last Glacial Maximum Eastern Beringia, northwest North America.

Potential Last Glacial Maximum (LGM, 26,500–15,000 bp) members of the Eastern Beringia (now Alaska-Yukon, northwest North America) vascular flora were recognized based on their contemporary co-occurrence in easternmost Siberia (formerly part of Western Beringia). Of 1,633 indigenous terrestrial Alaska-Yukon taxa, 835 also occur in easternmost Siberia, including 526 arctic/alpine and 90 subarctic taxa. Archival macrofossil and DNA evidence corroborated the occurrence of 55 LGM taxa and indicated the presence of an additional 13 non–Western Beringian taxa. The total (848) was double the number of taxa previously considered amphi-Beringian, but likely, still an underestimate. Most Eastern Beringian arctic/alpine and subarctic taxa were perennials (94%) and forbs (64%), with herbaceous plants having average median heights of ≤ 37 cm. Arctic/alpine taxa were associated with xeric to submesic environments (54%), whereas the subarctic taxa favoured moister conditions. Both arctic/alpine and subarctic taxa were potentially present in unglaciated Eastern Beringia. However, some subarctic taxa may have migrated from refugial areas peripheral to Western Beringia during the Late Wisconsinan, prior to opening of the Bering Strait (11,000 bp), rather than being migrants from mid-latitude North America because of timing and distance considerations. Currently, former LGM Eastern Beringian taxa dominate (> 80% content) the flora and plant canopy cover of Alaska-Yukon arctic vegetation, but their frequency decreases curvilinearly (~ 0.102 taxon km−1) from Alaska to Hudson Bay, and from Yukon to southern British Columbia (p < 0.05). More than half of these taxa occur > 1,400 km from Eastern Beringia. [ABSTRACT FROM AUTHOR]