| Summary: | The Antarctic climate is warming at an accelerating rate, driving the retreat of continental ice sheets in Antarctica. This decline in glacial formations relaxes dispersal barriers and allows the distribution ranges of terrestrial plant species to spread further inland and toward higher latitudes. At higher latitudes, species must adapt to the more extreme seasonal variation in day length. Thus, an extreme light environment may function as a bottleneck for the successful establishment of species in these areas. In this thesis, I studied the adaptability of Antarctic hairgrass, Deschampsia antarctica, in response to two latitudes characterized by differences in the seasonal variability of day length and temperature. I conducted a common garden experiment at two sites in Finland: Ruissalo, Turku (60°26'N) and Kevo, Utsjoki (69°45'N). These sites represent the current and future day-length conditions experienced by D. antarctica as the species disperses to higher latitudes. The study design consisted of plants collected from populations of two origins: southern Patagonia and coastal Antarctica. Despite fewer Antarctic replicates, it was possible to compare differences in the performance of plants from two genetic backgrounds in response to two latitudinal environments. To analyze these differences, I recorded plant growth and fitness-correlated traits over two consecutive growing seasons in 2022 and 2023. The results of this study demonstrate that D. antarctica is not restricted by the light environment in establishing and regulating its reproductive timing at higher latitudes. I found evidence of divergent adaptation between the two plant origins and latitudes in the initial growth following transplantation. This supports my hypothesis that genetic background affects the plants’ acclimatization to different light environments. Furthermore, the two sites and plant origins diverged significantly in survival and flowering rates. These results support previous studies of genetic distinctiveness between D. antarctica ...
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