| dc.description.abstract | Nearly one third of the vascular plant species of the remote high arctic archipelago of Svalbard are listed on the regional Red List for Svalbard, and there is a need for information to evaluate their conservation status, and improve conservation management. Here I study distribution, population sizes, ecology, and threats in Carex capillaris, Comastoma tenellum, Puccinellia angustata ssp. palibinii, and Tofieldia pusilla which are all restricted to some of the warmest local areas of Svalbard. Further, I use Amplified Fragment Length Polymorphism (AFLP) to evaluate whether the Svalbard populations are genetically depleted compared to other arctic-alpine populations of the species, investigate their phylogeographic history, and resolve taxonomic problems. All species have larger populations than previously assumed and new populations of C. tenellum and T. pusilla were discovered. Carex capillaris is thriving, and is associated with high substrate moisture and temperature at its only Svalbard locality. Local expansion potential was indicated. The population is genetically depleted, and forms a distinct genetic subgroup of ssp. fuscidula, with N Norway as the most likely source region. The results indicate that C. capillaris may have colonized Svalbard during the warmer early-middle Holocene, but a more recent introduction is also possible. Possible threats include reduced evolutionary potential, inbreeding depression, and stochastic events. Comastoma tenellum is growing in bird cliff vegetation at its three known localities. The populations are genetically depleted, and although clearly related to the most probable source region, NW Russia, they form a distinct genetic subgroup. This suggests an early-middle Holocene introduction of the species to Svalbard, associated with a strong founder effect. Possible threats include reduced evolutionary potential, inbreeding depression, and fluctuating population sizes. The population of P. angustata ssp. palibinii in Bockfjorden has been erroneously classified and belongs to the Svalbard endemic P. svalbardensis. This species exhibits a highly specialized ecology and is locally abundant in other parts of Svalbard. High levels of genetic diversity were detected, and no genetic threats are apparent. Tofieldia pusilla is found in different types of habitats, but temperature might restrict local expansion. The populations are not notably genetically depleted, which indicates that T. pusilla is doing comparatively better than many other thermophilous vascular plants in Svalbard. Based on the results, C. capillaris and C. tenellum were downgraded to less critical Red List categories, and T. pusilla was taken out of the Red List. As temperature probably is the limiting factor to C. capillaris, C. tenellum and T. pusilla in Svalbard, they are expected to benefit from a warmer climate. | eng |