The moss genus Didymodon as an indicator of climate change on the Tibetan Plateau

Bryophytes are sensitive to changing atmospheric conditions. Potentially, typical alpine bryophytes are valuable indicators of climate change for alpine ecosystems. However, little is known about the effects of climate change on the dominant alpine bryophytes of the Tibetan Plateau. In this study, we compared suitable habitats and predicted the effects of key environmental variables, in three climate change scenarios (RCP 2.6, RCP 4.5 and RCP 8.5), on the distribution of two dominant moss genera, a typically alpine xerophytic functional group, Bryoerythrophyllum and Didymodon in Pottiaceae. We used Maximum Entropy model (MaxEnt) modelling, for the 2050s and 2070s in Tibet. Simulation-based estimates suggest that Bryoerythrophyllum are more suited to habitats from semi-humid regions to semi-arid regions while Didymodon are relatively drought-resistant mosses that mainly inhabit drought regions. The variables associated with temperature will have the strongest effect on the future distribution patterns of both Bryoerythrophyllum and Didymodon when compared with precipitation and topographic variables. However, Climate change should affect Didymodon the most, due to its relatively narrow temperature and precipitation range for optimum growth. Additionally, Bryoerythrophyllum is predicted with a ratio of increase in suitable areas at 19.08%, 141.49% and 121.56% and 55.22%, 129.93% and 172.08% under all three scenarios, for 2050 and 2070, respectively. In contrast, Didymodon has a ratio of increase in suitable areas at -25.36%, 12.51% and 51.1% and 13.71%, 14.27% and 131.91%, for all three scenarios for the two future decades, respectively. However, there are more obviously regular expansions and contractions can be easily caught for Didymodon than for Bryoerythrophyllum with GHG emissions from low to high. In summary, although Bryoerythrophyllum and Didymodon are evolutionarily closely related and have similar distribution patterns and future upward and northward shifts, Didymodon will respond more to climate warming under each climatic scenario for the 2050s and 2070s. Therefore, Didymodon is recommended as an indicator of climate change on the Tibetan Plateau.