Phylogeography of Arctic plants: where are we after 35 years, and where to go?

Abstract

Background: The Arctic provides an excellent system to study climate change effects on geographic ranges and genetic diversity. We re-examine the large number of phylogeographic studies of Arctic plants to assess general patterns and identify knowledge gaps. Aims: To synthesise advances and address century-old controversies, e.g. is it necessary to invoke separate glacial refugia to explain Arctic disjunctions? Methods: We undertook a literature survey of the phylogeography of Arctic vascular plants. Results: We provide a list of 88 taxa studied, representing a striking diversity of phylogeographic histories. In many widespread species, recent trans-oceanic long-distance dispersal (LDD) is sufficient to explain disjunctions, but three rare species show clear signals of separate Scandinavian and American glacial refugia. The extreme bipolar disjunctions are apparently caused by Plio-Pleistocene LDDs. Beringia and western Siberia have served as long-standing northern refugia; in contrast, North Atlantic areas harbour much less genetic diversity and distinctiveness. The genomic era is now providing evidence for multiple refugia from modern and ancient DNA and demonstrating that selfing leads to high biological species diversity within taxonomically recognised species. Conclusions: More extensive sampling, reference genomes, and population genomic studies are required for in-depth understanding of past distributions, dispersal routes, and ability to track ongoing climate change.