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Systematic and biogeographical relationships within the Hawaiian clade of the pantropical understory shrub genus Psychotria (Rubiaceae) were investigated using phylogenetic analysis of 18S–26S ribosomal DNA internal (ITS) and external (ETS) transcribed spacers. Phylogenetic analyses strongly suggest that the Hawaiian Psychotria are monophyletic and the result of a single introduction to the Hawaiian Islands. The results of phylogenetic analyses of ITS and ETS partitions alone give slightly different topologies among basal lineages of the Hawaiian clade; however, such differences are not well supported. Relationships in the section Straussia clade in particular are not well resolved because of few nucleotide changes on internal branches, suggesting extremely rapid radiation in the lineage. Parsimony and likelihood reconstructions of ancestral geographical distributions using the topologies inferred …