New species and a new lectotypifications in Forsteronia (Apocynaceae, Mesechiteae)

Four new species of Forsteronia are described and illustrated, a distribution map and a key for the species of Forsteronia in Brazil provided, and Forsteronia myriantha lectotypified. Forsteronia manausana resembles F. brevifolia , but differs by its glabrous filaments and smaller leaves. Forstersonia nitida shows affinity to F. tarapotensis but is distinguished by the combination of subcoriaceous, elliptic leaves, large-bracted inflorescences, and somewhat larger flowers . Forsteronia paraensis is apparently most closely related to F. laurifolia but can be separated by its larger and more heavily veined leaves, longer and more floriferous inflorescences, and pubescent ovaries. Forsteronia prancei is morphologically similar to F. manausana , from which it is distinguished by the larger and more coriaceous leaves, denser and more hemispheric inflorescence, and larger flowers.