Ayenia nathaliae (Malvaceae, Byttnerioideae), a new species from Colombia and three new combinations

Ayenia nathaliae Dorr, sp. nov. is described and illustrated, and its relationships are discussed. It is known only from the Magdalena Medio subregion of Antioquia department, Colombia. Morphologically, it is similar to A. saligna Dorr, another Colombian endemic from the Bajo Cauca and Nordeste subregions of Antioquia and also restricted to riparian habitats.

The new species is tentatively assigned to A. subsect. Stipulares Cristóbal, an early diverging lineage of species within Ayenia s. str. found in northern South America and Central America. However, the boundaries of this subsection and other subsections are unclear.

In addition, after reviewing the species of Ayenia L. and Byttneria Loefl. known from Colombia, three additional species of the latter genus are transferred to the former.