Diversity trends of bryophytes in Antarctica are the result of adaptation, evolution and survival (including cryptobiosis): the case study of the phylogeny of Bryum argenteum

• Main Authors: Nicoletta Cannone, Isabella Vanetti, Omar Rota-Stabelli, Peter Convey, Francesco Malfasi, Paolo Gerola, Alberto Vianelli, Mauro Guglielmin, Serena Zaccara
• Other Authors: Nicoletta Cannone, Isabella Vanetti, Omar Rota-Stabelli, Peter Convey, Francesco Malfasi, Paolo Gerola, Alberto Vianelli, Mauro Guglielmin, Serena Zaccara, Cannone, Nicoletta, Vanetti, Isabella, Rota-Stabelli, Omar, Convey, Peter, Malfasi, Francesco, Gerola, Paolo, Vianelli, Alberto, Guglielmin, Mauro, Zaccara, Serena
• Format: Conference Object
• Language: English
• Published: Società Botanica Italiana 2018
• Subjects: Moss; Antarctica; Antarctic; Antarctic Peninsula; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/11383/2079360; http://www.societabotanicaitaliana.it/uploaded/6165.pdf

Terrestrial vegetation communities in Antarctica are predominantly composed by bryophytes and lichens, as the extreme climatic conditions of this remote continent limit the colonization of vascular plants to 2 species in the Antarctic Peninsula. A decline in bryophyte species richness occurs with latitude across the sub-Antarctic islands, Antarctic Peninsula and Antarctic continent, with a clear continent-Antarctic Peninsula separation, consistent with the Gressitt Line, a boundary identified for the invertebrate fauna, and now demonstrated also for bryophytes, suggesting a common feature in the evolutionary history of the vegetation and invertebrate fauna. Within continental Antarctica, the highest bryophyte diversity occurs in the Ross sector, despite its location is the least favorable for species migrating from the southern Hemisphere continents. Moreover, the occurrence in Antarctica of cosmopolitan species, such as Bryum argenteum, further highlights the need to understand the origin and evolution of the Antarctic flora and to investigate the role of Antarctica in explaining the dispersal routes of taxa with transoceanic or transcontinental disjunctions, with B. argenteum being an ideal target species. We reconstructed the phylogeny and divergence times of B. argenteum, both at global scale and focusing within Antarctica and Southern Hemisphere, using the nrITS region from more than 200 samples applying a molecular clock based on previously estimated substitution rates for mosses. Our analyses indicate that the distribution patterns of B. argenteum, at global scale, are the result of major paleoclimatic events occurring across the planet, and involving differentiation and migration/colonization during periods warmer than today since the Mid Miocene Climate Optimum (MMCO), as well as fragmentation during severe cooling, such as during the extensive Antarctic glaciations in the mid Miocene 14 Ma. Bryum argenteum first extensively colonized Antarctica around 9.77 Ma during the warm Tortonian (Miocene), using ...