A Phytogeographically Significant New Species of Jatropha (Euphorbiaceae) from Costa Rica

Abstract

Jatropha costaricensis is described from Guanacaste, Costa Rica and assigned to sect.Platyphyllae. It is most similar toJ. alamanii of the Isthmus of Tehuantepec in Mexico, and represents part of a secondary Central American radiation of xeric-adapted Euphorbiaceae. Its geographic relationships indicate a formerly more widespread occurrence of a tropical deciduous flora in Mesoamerica, and it is suggested that xeric range disjunctions here and in adjacent South America may be largely due to climaticallyinduced extinction rather than to long-distance dispersal.