Richness and Scarcity of the Flora of White Sea Islands

This paper provides basic information about the flora of vascular plants on more than 100 islands in the White Sea. The islands differ in size, remoteness from the mainland, aggregation into archipelagos, coastline serration, freshwater bodies and watercourses, geological structure and age, and human pressure. In total, over 700 species of vascular plants have been recorded from the islands. The number of native species varies from zero on rocky islets to 337 on Bolshoi Solovetsky Island. This depends mainly on the island's area, and to a lesser extent on isolation, geological structure, and coastline serration. On smaller and more remote islands, significant deviations from the ”basic” taxonomic and geographical structure of the local boreal flora occur due to a gradual decrease in the proportion of boreal species and an increase in the proportion of species with a more northern distribution. The role of the Poaceae family increases sharply in the taxonomic spectrum. In the geographical structure, the distribution of latitudinal fractions changes significantly - the share of species with a northern distribution increases to 43%. The taxonomic structure and ratio of geographic elements of many island floras are similar to those of islands in northerner (more arctic) latitudes. Keywords: White Sea, island, vascular plants, biodiversit