Abstract. Specialists studying the genus Viola have consistently allied the Hawaiian violets comprising section Nosphinium-most of which are subshrubs or treelets-with putatively primitive subshrubs in certain South American violet groups. Hawaiian violets also possess inflorescences, a floral disposition otherwise found only in other genera of the Violaceae, thus strengthening the hypothesis of a very ancient origin for the Hawaiian species. A survey of phylogenetic relationships among infrageneric groups of Viola worldwide using nuclear rDNA internal transcribed spacer (ITS) sequences revealed a dramatically different biogeographic origin for the Hawaiian violets: A monophyletic Hawaiian clade was placed in a close sister relationship with the amphi-Beringian tundra violet, V. langsdorffii s. l., in a highly derived position. This remarkable and unforeseen relationship received strong clade support values across analyses, and monophyly of the Hawaiian lineage was further indicated by a unique 26-base-pair deletion in section Nosphinium. The high polyploid base chromosome number (n Ӎ 40) in the Hawaiian violets relates them to Alaskan and eastern Siberian populations in the polyploid V. langsdorffii complex. More than 50 species of the 260 allochthonous birds wintering in the Hawaiian Islands are found to breed in the Arctic, occupying habitats in which individual birds might have encountered ancestral V. langsdorffii populations and served as dispersers to the central Pacific region. Acquisition of derived morphological traits (e.g., arborescence and inflorescences), significance of a confirmed Arctic origin for a component of the Hawaiian flora, and the likelihood of other ''cryptic'' Arctic elements in the Hawaiian flora deserving independent molecular phylogenetic corroboration are discussed. Extraordinary geographic isolation of the Hawaiian archipelago (more than 3500 km from the nearest continent), a diverse flora of nearly 1000 native angiosperm and approximately 180 pteridophyte species, and an unparalleled 86% endemism in angiosperms and about 70% in pteridophytes (Wagner et al. 1990;Sakai et al. 1995;Wagner and Funk 1995) make the Hawaiian flora one of the most tantalizing foci for evolutionary inquiry. Earlier explicit inferences on the minimum number of successful colonizations responsible for the modern-day Hawaiian vascular flora (Fosberg 1948;Carlquist 1970) have recently been updated to 291 putative events for angiosperms and an additional 115 for pteridophytes (Wagner 1991;Sakai et al. 1995). The Hawaiian flora thus offers unique opportunities for biogeographic and evolutionary studies of oceanic island systems (Carlquist 1965(Carlquist , 1974Wagner and Funk 1995;Givnish 1998). Comprehensive higher-level phylogenetic studies including endemic Hawaiian plants have the potential to elucidate the biogeographic origins of those plant groups and reevaluate previous hypotheses of dispersal and character evolution. Well-established geologic dates pinpoint the time of origin of islands that formed ''c...