Physiological and molecular responses of Antarctic mosses under experimental warming.

Antarctic ecosystems are undergoing rapid environmental change, yet the physiological and molecular mechanisms by which dominant moss species respond to warming remain poorly understood. This thesis explores species-specific responses of Antarctic mosses to increased temperatures, integrating field and laboratory experiments to assess carbon flux dynamics and differential gene expression. In the field experiment, open-top chambers (OTCs) were used to simulate natural warming, allowing for in situ measurements of gross ecosystem productivity, net ecosystem exchange, and ecosystem respiration across multiple species. In the laboratory experiment, controlled growth chambers mimicked Antarctic temperature fluctuations, enabling precise assessments of physiological acclimation and transcriptomic shifts under warming conditions. Physiological data revealed contrasting responses among species, with Sanionia uncinata and Polytrichum juniperinum maintaining stable photosynthetic and respiratory rates under warming, while Bryum argenteum and Chorisodontium aciphyllum exhibited significant declines in carbon assimilation. Transcriptomic analyses further demonstrated species-specific acclimation strategies, with resilient species upregulating stress-response genes and antioxidant enzymes, whereas vulnerable species showed downregulation of photosynthetic machinery and energy metabolism pathways. These findings suggest that warming may favor metabolically flexible species, potentially reshaping moss community composition and carbon sequestration capacity in Antarctic ecosystems. By integrating ecosystem-scale carbon flux measurements with molecular-level gene expression data, this study provides novel insights into the adaptive capacity of Antarctic mosses under climate change. The results highlight the importance of species-specific strategies in determining ecosystem resilience, with broader implications for predicting shifts in polar vegetation dynamics and carbon cycling under future warming scenarios.