Harpochilus neesianus and other novel cases of chiropterophily in neotropical Acanthaceae

(Uploaded by Plazi for the Bat Literature Project) Floral adaptation to pollination by bats is rare in Acanthaceae and only known from neotropical species. Two novel cases are described in detail from field observations. Harpochilus neesianus, a shrub endemic in NE Brazil, with long emergent thyrses, was seen being regularly visited by hovering glossophagine bats (Glossophaga soricina). Its large, pale lemon-green corollas are strongly bilabiate, a shape uncommon in the syndrome. The lower lip segments are recurved and the upper lip is reduced to a narrow, arcuate, tubular organ serving to support stamens and style. A sour, cabbage-like odour is released, and copious nectar is secreted by a voluminous disk. Pollen is transferred by the bat's upper, rear surface. Anthesis is confined to a single night. Chiropterophily in Ruellia eurycodon is deduced from the floral syndrome. The flowers of this shrub, studied in Goyás, Central Brazil, share the same features as Harpochilus except for the corolla shape, which conforms to the "short bell type" frequent in neotropical bat flowers. Based on literature sources, bat pollination is also predicted for Ruellia malaca and R. exostemma from Venezuela. The occurrence of this floral type in other genera of the family is briefly surveyed.