Evidence of reward production and pollination by Centris in Encyclia (Orchidaceae: Laeliinae): the reproductive biology of Encyclia mapuerae

Abstract

Encyclia is a neotropical orchid genus distributed from Florida to South Brazil and comprises ∼120 taxa, including Encyclia mapuerae (Huber) Brade & Pabst. Besides its diversity and wide distribution, conclusive data on pollinators and reproductive biology of this orchid genus is scarce. Furthermore, nothing is known about the production of floral reward in Encyclia but the pollinators of their species are assumed to be attracted through food deception. Based on data on phenology, floral morpho-anatomy, histochemistry, pollinators, pollination mechanisms, and breeding system, the reproductive biology of E. mapuerae was studied in a nature reserve at Central Amazonia, Brazil. The flowers of E. mapuerae show longitudinal lines on the labellum that act as a nectar guide. The secretory epidermis has papillae whose cells are covered by an ornamented cuticle. The subtended tissue is composed of a tree-layered collenchyma. The flowers attract several species of Hymenoptera. However, a single species of Centris was recorded as pollinator. The bees collect the nectar produced inside the cuniculus. When the bees leave the flower the pollinarium is attached to their heads. Encyclia mapuerae is self-compatible and pollinator-dependent. The reproductive success in natural conditions is low because of deficient pollen transference due to the scarcity of pollinators. As far we know this is the first study that reports and production of floral reward in Encyclia. This discovery provides new insights on the function of the cuniculus in Laeliinae, and sheds light on the evolution of floral rewards and pollination mechanisms within this diverse group of Neotropical orchids. © 2017 CSIRO.