Chromosome numbers, ploidy levels, and available genome size data of Svalbard plants

Accurate estimation of genome size and determination of ploidy levels are fundamental for understanding plant genome architecture and their adaptive strategies in extreme environments. The Arctic region of Svalbard hosts a distinct vascular plant flora adapted to harsh climatic conditions, but comprehensive cytogenetic data remain scarce. This study compiles and analyzes chromosome numbers, ploidy levels, and genome sizes (C-values) for 185 plant taxa of Svalbard, providing essential baseline data for evolutionary and ecological research. Chromosome counts in Svalbard flora range from 2n = 10 to 270, with modal base numbers of x = 7 and x = 8. Polyploidy is widespread, with diploids representing 67 taxa followed by tetraploids, hexaploids, and higher even ploids. Genome sizes (1C-values) exhibit considerable variation both within and between families. Notably, chromosome number and genome size are decoupled in Cyperaceae and Poaceae, attributed to the difference of chromosome size. The prevalence of polyploid taxa is linked to increased genetic diversity and potential epigenetic mechanisms promoting survival in the Arctic's cold, nutrient-poor, and short growing season environments. This comprehensive cytogenetic dataset provides a critical foundation for ongoing and future studies on plant adaptation, evolution, and genome dynamics in Arctic ecosystems. The findings underscore the ecological importance of polyploidy and genome structural variation in shaping the resilience of polar flora under climatic stress and global change. These data will enhance molecular, ecological, and conservation research efforts in Svalbard and other high-latitude regions.