The last refugia for a polar relict pollinator: isolates of Bombus glacialis on Novaya Zemlya and Wrangel Island indicate its broader former range in the Pleistocene

Bombus glacialis Friese, 1902 is an Arctic bumblebee that was thought to have a disjunctive range on the Arctic Ocean Islands, i.e., on Novaya Zemlya and Wrangel Island, with a 3600 km gap between these isolates. While the species status of the Novaya Zemlya’s population was recently confirmed using a molecular approach, its close affinities to the Wrangel’s isolate were proposed by a morphological similarity alone. Here, we report that B. glacialis samples from Wrangel share three unique COI haplotypes, which are closely related to each other and to those inferred from samples from Novaya Zemlya. Based on a combination of diagnostic morphological and molecular characters, the Wrangel’s population is described here as a new subspecies, Bombus glacialis marinae ssp. nov. Our novel data indicate that this species can be considered a polar relict that had had a much broader distribution along the continental margin of Eurasia during the Pleistocene. The two subspecies of B. glacialis were likely separated in the Middle Pleistocene (mean age = 0.27 Myr, 95% CI = 0.12–0.46 Myr) due to increasing of the sea level during an interglacial. The Novaya Zemlya Archipelago supported a B. glacialis population in the Late Pleistocene. Hence, this insular land was not covered completely by ice sheet during the Last Glacial Maximum. Our findings highlight that relict cold-adapted Pleistocene lineages still survive on remote islands in the Arctic Ocean and that such lineages are highly threatened by recent climate warming.