Abstract
A new species of Apocynaceae, Rauvolfia anomala Rapini & I. Koch, is described and illustrated. It was found in low savanna of Chapada dos Guimarães, Mato Grosso state, sympatric with R. weddelliana. The two species seem to be closely related, but can be easily distinguished by the flowers, whose corolla is greenish, with lobes longer than the tube in R. anomala, or reddish with lobes shorter than the tube in R. weddelliana. The new species has remarkable floral polymorphism and possibly represents a new example of dioicy in the genus. This is the first species of Rauvolfia with narrow distribution reported to Mato Grosso.
Key words:
dioicy; Neotropics; Rauvolfioideae; Central-West Region