Evolução floral das Malpighiaceae: o que as glândulas do cálice de espécies africanas e asiáticas revelam?

Abstract

Malpighiaceae is a pantropical family in neotropical species, calyceal glands in pairs secrete oil (elaiophores), offered to bees, while paleotropical species have nectariferous glands. To understand the floral evolution in this family, the present work aims to record unpublished data on calyx glands in paleotropical species of Hiptage Gaertn. and Tristellateia Thouars. The samples were obtained from a herbarium and after reversal of herborization, the distribution pattern of the glands was observed and outlined in drawings. The samples were embedded in historesin, sectioned, and the slide mounted according to the usual methodology. The results in Hiptage showed glands developed with an elongated to circular shape, whereas in Tristellateia these are small and globular. The distribution pattern in Hiptage varies from one to three glands located in the intersepalar region, while in Tristellateia from one, two to ten glands on the margin of the sepals. Anatomy revealed typical composition, with palisaded secretory epidermis and vascularized secretory parenchyma. The intrageneric variations recorded, in contrast to the well-preserved stereotype observed in the elaiophores of neotropical species, corroborate the role of selective pressure of collector bees in the maintenance of neotropical morphology. Therefore, with changes in the pollination syndrome, the calyx glands reveal variations and probably function as nectaries.