Systematic relationships among various African (including Malagasy) and American (including West Indian) Acanthaceae recently have been shown to be closer than previously believed; several pairs of amphiatlantic genera, formerly treated as endemic to their respective hemispheres, have been shown to be congeneric. Barleria is a mostly paleotropical genus of about 300 species. Tropical eastern Africa is particularly rich in species of Barleria. Traditionally, a single endemic species has been recognized from the New World. Recently, this species has been shown to be conspecific with B. oenotheroides, a native of tropical western Africa. Barleria oenotheroides is presumed to be native in America based, in part, on its extensive distribution in and early documentation from the neotropics. It appears to be the only species of Acanthaceae thought to be native to both Africa and America and, indeed, to both the Old World and the New World. Information on chromosome numbers, nectar-sugar composition, pollinators, and dispersal mechanisms is compared between Barleria in America and the Old World. The present phytogeographic links among Acanthaceae in Africa, Madagascar, India, and South America are indicative of a "Gondwanan" distribution pattern for the family and suggest an early radiation in southern land masses. Close taxonomic affinity among plants in these regions indicates that a global perspective is needed in resolving systematic relationships among the more than 225 genera of Acanthaceae.

Key words: Acanthaceae, B. oenotheroides, Barleria, phytogeography