Ancient macrofossil remains investigated in the study.

Authentic DNA sequence obtained from: CFx3.4, CFx3.8 and CFx3.11.
14C yr. BP) radiocarbon years before present (1950); p.p.) posterior probability of assigning the sequence to the given taxonomic level. The species Amara alpina is also known as Curtonotus alpinus (Paykull, 1790) in some literature. Lepidophorus thulius was until recently known as Vitavitus thulius Kissinger, 1974.
Alaska sample ages estimated from radiocarbon dates of associated plant macrofossil ages from sampling horizon. Chukotka sample ages estimated from sedimentation rate based on overlying and underlying radiocarbon dated samples of plant macrofossils (See Materials and Methods section).