Neotropical species of the Adiantum raddianum group (Pteridaceae)

As recently demonstrated, the group of Adiantum raddianum is monophyletic and can be recognized by round-reniform indusia and veins ending in sinuses at the sterile segment margins. The most related species belong to the A. poiretii group, which is morphologically distinct by the oblong to Innate indusia. In the A. raddianum group sixteen species are recognized in the present work. Among these species, A. patens s.l. is the unique species that occurs in Africa outside the neotropical region. Adiantum raddianum is the broadest distributed species of the group, widely cultivated globally, and it has become naturalized in the Paleotropics and other regions. Typifications are presented for two accepted names: A. lorentzii and A. ruizianum. Several other typifications are also presented for synonymized species. Adiantum alan-smithii, A. galeottianum, A. imbricatum, A. lobatum, A. ruizianum, A. shepherdii and A. subvolubile are species with restricted distributions occurring only in one or two countries. An identification key, as well as descriptions, synonymies, discussion on morphology and taxonomy, illustrations and a list of specimens examined are provided.