A New Flagelliflorous Species of Stenanona (Annonaceae) from Mexico, with a Review of the Phenomenon of Flagelliflory

Abstract

Stenanona flagelliflora is described as a new species of small, flagelliflorous tree from deep-soil hill rain forests of the Uxpanapa-Chimalapa region of the Isthmus of Tehuantepec, in Veracruz and Oaxaca, Mexico. In flagelliflory, flowers are borne on essentially leafless modified whip-like branches that trail across the ground; this is the first report of the phenonenon for the flora of Mexico or Central America. The phenomenon of flagelliflory and its worldwide occurrence are reviewed. The Central American genus Stenanona is not closely related to other New World annonaceous genera with flagelliflorous species but rather is likely most closely related to the Old World species of Polyalthia with superficially inaperturate but internally disulculate pollen. The distribution of S. flagelliflora and of its closest relatives, as well as the existence of flagelliflory in Mexican rain forest, provide additional data supporting the persistence of rain forest lineages in Mexico throughout climatically adverse periods of the late Cenozoic. The new species is considered to be Critically Endangered (CR) under the IUCN Red List classification.