Cryptic speciation shapes the biogeographic history of a northern distributed moss.

This article investigates the phylogeographic history and cryptic speciation within the widely distributed northern moss Racomitrium lanuginosum across the Northern Hemisphere. Using nuclear internal transcribed spacer (ITS) sequences and genotyping-by-sequencing (GBS) single nucleotide polymorphisms (SNPs), the study identifies three major ITS clades and four SNP-based genetic groups that are sympatrically distributed, indicating the presence of cryptic molecular lineages. Molecular dating suggests divergence around 5 million years ago, with evidence of long-distance dispersal from eastern North America to Scandinavia and potential glacial refugia in the Alaska Peninsula and Scandinavian Mountains during the Last Glacial Maximum. Species distribution models support a contraction of suitable habitats during glaciations followed by post-glacial northward expansion, highlighting complex demographic processes shaping the genetic diversity and biogeography of this Arctic and sub-Arctic moss.