Morales, J.F. 2100. Studies in neotropical Apocynaceae XL: synopsis of the genus Prestonia (Apocynoideae, Echiteae) in Ecuador. Anales lard. Bot. Madrid. 67(1): 13-21 (in Spanish). A synopsis of the genus Prestonia (Apocynaceae, Apocynoideae, Echiteae) in Ecuador is presented and 15 species are reported. A key to species, distributional data, discussion of relationships, and representative specimen citations for each province are provided. An illustration of the enigmatic P. schumanniana Woodson, known only from the type collection, is also included. Prestonia purpurissata Woodson, P. phenax Woodson, P. peregrina Woodson y P. vallis Woodson are reduced to the synonymy of P. annularis (L. f.) G. Don and Echites pallidus Miers to the synonymy of P. mollis Kunth. Lectotypes are designated for Haemadictyon tomentellum Benth., Prestonia phenax Woodson, and P. plumierifolia Markgr. A neotype is designated for P. vallis Woodson.