Sequences of the internal transcribed spacers (ITS) of nuclear ribosomal DNA were acquired for 112 species of Balsaminaceae worldwide and five species of its closest relatives Marcgraviaceae and Tetrameristaceae. Phylogenetic analyses applying parsimony and distance estimates confirmed the monophyly of Balsaminaceae and suggest the monophyly of Impatiens. Within Impatiens, a few clades are recognized with strong support. Two of the most important clades are the spurless Madagascan endemic group, and the one comprising species with broadly fusiform fruits and the basic chromosome number x = 8, that shows a Southeast Asia, southern India, Africa, and Madagascar connection. Despite recognition of several strongly supported small lineages, ITS data alone could not resolve relationships among most of the lineages with confident support values. ITS phylogenies are therefore of limited taxonomic value for Impatiens. However, ITS phylogenies do reveal that extant Impatiens species are of Southeast Asian origin, from where dispersals to boreal Eurasia and North America, to central Asia and eastern Europe via the Himalayas, and to India and Africa have occurred. The Madagascan Impatiens show an African origin. Molecular phylogenies suggest the ancestral basic chromosome number to be x = 10, and the spurred flowers and elongated linear fruits to be plesiomorphic states in Impatiens. A predominantly descending dysploid chromosome evolution, following dispersal of the clade with broadly fusiform fruits from Southeast Asia to India, Africa, and Madagascar, is also suggested.

ABSTRACT. Balsaminaceae are a morphologically diverse family with ca. 1,000 representatives that are mainly distributed in the Old World tropics and subtropics. To understand the relationships of its members, we obtained chloroplast atpB-rbcL sequences from 86 species of Balsaminaceae and five outgroups. Phylogenetic reconstructions using parsimony and Bayesian approaches provide a well-resolved phylogeny in which the sister group relationship between Impatiens and Hydrocera is confirmed. The overall topology of Impatiens is strongly supported and is geographically structured. Impatiens likely originated in South China from which it colonized the adjacent regions and afterwards dispersed into North America, Africa, India, the Southeast Asian peninsula, and the Himalayan region.

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