Increasing evidence indicates that wide distributed bryophyte taxa with homogeneous morphology may represent separate evolutionary lineages. The evolutionary histories of these cryptic lineages may be related to historical factors, such as the climatic oscillations in the Quaternary. Thus, the post-glacial demographic signatures paired with cryptic speciation may result in complex phylogeographic patterns. This research has two aims: to determine whether the widespread moss Racomitrium lanuginosum represents cryptic molecular taxa across the Northern Hemisphere and to infer the effects of Quaternary glaciations on spatial genetic diversity. We used the internal transcribed spacer (ITS) marker to resolve the phylogeographic history of the species and single nucleotide polymorphisms (genotyping-by-sequencing) to infer the genetic structure and demographic history. Finally, we assessed the historical changes in the distribution range using species distribution models. Racomitrium lanuginosum comprises distinct molecular lineages sympatrically distributed in the Northern Hemisphere. We also uncovered long-distance dispersal from eastern North America to Scandinavia and potential in situ survival in northern Scandinavia. Due to the genetic signatures, the Alaska Peninsula could be considered a glacial refugium. The species experienced post-glacial expansion northwards in the Northern Hemisphere, mainly from the Alaska Peninsula. Our results exemplify the complex phylogeographic history in cold environments and contribute to recognizing evolutionary patterns in the Northern Hemisphere.

Antecedentes y Objetivos: En México, los registros del género Notothylas se limitan a escasos reportes en la literatura y ejemplares de herbario. En este estudio, Notothylas javanica se reporta por primera vez para México.Métodos: Se examinaron los caracteres morfológicos de Notothylas javanica utilizando los microscopios estereoscópico, óptico y electrónico de barrido. Los ejemplares recolectados se depositaron en MEXU.Resultados clave: Se presenta la descripción, ilustración y datos ecológicos de la especie. Se discuten las diferencias y similitudes con las otras especies de Notothylas registradas para México. Adicionalmente, se presenta una clave para la determinación de las especies mexicanas de Notothylas.Conclusiones: La información disponible para Notothylas sugiere la presencia de al menos tres especies en México. A fin de incrementar el conocimiento del género en este país, se recomienda explorar zonas clave y, además, realizar estudios que permitan conocer su diversidad, ecología y distribución geográfica.

Bryophytes maintain symbiosis with epiphytic bacteria influencing the local nutrient budget. Moss bacterial communities are composed of a core microbiome and bacteria recruited from environmental sources. Notably, symbiotic N2-fixing bacteria contribute to the N budget in northern ecosystems through biological nitrogen fixation. This process may be affected by the abundance of diazotrophs and moss nutrient content. We used the abundant mossRacomitrium lanuginosumin a forest tundra and shrub tundra in Northern Quebec, Canada, to investigate the bacterial and diazotrophic communities associated with habitat type using amplicon sequencing of the bacterial 16S rRNA andnifHgenes and test whether the moss core microbiome has recruitment from the soil bacteria community. ThenifHamplicons and element analysis were used to test the effect of diazotrophic abundance and moss nutrient content on N2-fixation activity estimated by acetylene reduction assays. Moss microbial communities between tundra types hosted similar bacterial diversity but differentially abundant groups. The core microbiome ofR. lanuginosumis composed of bacteria strongly associated with northern mosses with no significant recruitment from the soil. The relative abundances of dominant diazotrophs are significantly correlated with acetylene reduction rates. In contrast, the moss nutrient content did not significantly drive N2-fixation. The proteobacterial generaAzorhizobiumandRhodomicrobiumrepresent newly reported bacteria associated with N2-fixation rates in the tundra. We identified critical bacterial groups related to moss-bacterial symbiosis and N2-fixation in the forest-tundra transition zone, a changing environment susceptible to climate warming.