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The species-rich flora of Madagascar is well known for a range of unusual floral ecologies. One example is Impatiens section Trimorphopetalum with its unique combination of floral traits: small, spur-less, cup- or lip-shaped, greenish or brownish flowers. So far no hypotheses on floral function or pollination of this peculiar group have been proposed. We analysed six reproductive traits in relation to pollination syndromes for 34 Madagascan Impatiens species, including 18 species of section Trimorphopetalum plus six outgroup species, in a phylogenetic framework. Further, we present pollinator observations for one additional species of Trimophopetalum. All pollination syndromes occurring in the African species are also present in Madagascan Impatiens. In addition, species of Trimorphopetalum represent two unique floral types, possibly corresponding to two different types of fly pollination. The evolution of these flower types corresponds to a strong decrease in nectar production, flower display size, pollen grain and ovule number. Autogamy is found in one derived sub-clade of the otherwise largely pollinator-dependent Trimorphopetalum. We find evidence consistent with the evolution of brood-site deception and fungus mimicry in combination with fly pollination in one clade of Trimorphopetalum and the stepwise evolution of autogamy in the second clade. The evolution of these very different reproductive strategies may have been triggered by pollinator limitation in the dense, humid forest undergrowth of Madagascar.

The new species Impatiens max-huberi is described from Mt. Marojejy. It is resembles Impatiens sambiranensis from Northwestern Madagascar in the large pink-purple flowers with long spur, but differs in the alternate leaves and the curved spur.

Two new species, Impatiens susan-nathansoniae and I. hendrikii, from Mt. Marojejy, Madagascar, are described. Impatiens susan-nathansoniae is related to I. humblotiana from eastern central Madagascar, but differs in the shape of the lower sepal with spur, the dorsal petal and the lateral united petals. Impatiens hendrikii is related to I. fuchsioides, but differs in the straight stem, the larger leaves, the broader lateral sepals, the broader lateral united petals with different shape, and the glabrous lower sepal gradually tapering into a short, saccate, whitish red spur.

Impatiens lutzii, a new species of Impatiens subg. Trimorphopetalum, is described from Montagne d’Ambre, Madagascar. It is morphologically similar to Impatiens luisae-echterae, I. callmanderi and I. silviana from Masoala, and to I. decaryana from central Madagascar, but differs from these species in the shape and ornamentation of the lower sepal, as well as the shape of the dorsal petal and the lateral united petals. A comparative table to distinguish I. lutzii from similar species of Impatiens is provided.

The new species Impatiens otto-eleonorae Eb.Fischer & Rahelivolona from Masoala Peninsula is described. It is related to Impatiens hildebrandtii Baill. from Eastern Central Madagascar, but differs in the larger habit and flowers. The types of Impatiens firmula Baker and I. hildebrandtii are reinvestigated. Both taxa, previously considered to be identical, represent different species, and Impatiens hildebrandtii is reinstated here.