Molecular analyses support revision of species diversity of the moss genus Bryum in Antarctica

Bryum is a moss genus that is widely distributed across the planet. Many of its species are characterized by large phenotypic and morphological plasticity, generating uncertainty in species identification exclusively based on morphological characteristics. In Antarctica, the extreme and harsh environmental conditions are further likely to promote intra-specific morphological variation, leading to complexity in the taxonomic attribution of Bryum species. In this study, we apply molecular phylogenetic analyses to assist in developing accurate species identification of B. pseudotriquetrum and two other relatively abundant Bryum species (B. archangelicum and B. pallescens) currently reported as Antarctic species. A total of 51 Bryum samples collected in Antarctica (22) and from all other continents (29) were sequenced for ITS nrDNA and rps4 cpDNA regions, using markers widely used in moss phylogenetic studies. Phylogenetic trees were constructed including ITS (23) and rps4 (34) sequences representing the three more frequent of the seven Bryum species currently reported from Antarctica as well as several other Bryum species and related genera, incorporating all sequence data available in the literature and accessible databases. The molecular analyses provide strong support for a match between morphological and molecular attribution of specimens identified as B. pseudotriquetrum. The data also provide evidence of currently unrecognized Bryum diversity in Antarctica, with the identification of one individual of B. uliginosum. However, the analyses suggest that all Antarctic specimens currently assigned to other Bryum species are morphological variants of B. pseudotriquetrum. The integration of molecular and morphological analyses supports the presence of B. pseudotriquetrum as the most widely distributed species of the genus in Antarctica and of B. uliginosum with a much more restricted distribution (South Sandwich Islands). Our data suggest that further investigation is required of B. archangelicum and B. pallescens in other continents globally, as the identity of none of the herbarium specimens examined in this study could be confirmed with molecular data.