Specificity and influence of climatic factors on the pollination of south-eastern Brazilian Sinningia

Abstract

Ornithophily is a widespread pollination syndrome that has evolved independently several times along the evolution of plants. It is reported in sixty-five plant families, including Gesneriaceae. One of the most diverse genera within gesneriads is Sinningia, which comprises species pollinated by bees, hummingbirds and bats. However, little is known about the reproduction biology of either species or on pollinator specificity in this genus. Based on investigations on flowering phenology, flower morpho-anatomy, volume and concentration of floral nectar, pollinators, and breeding system, this paper reports the reproduction and the pollinator specificity of Sinningia douglasii and Sinningia araneosa in natural areas in Brazil. Both species offer nectar as a resource and are exclusively pollinated by a single species of hermit hummingbird. Nectar is produced by glands around the ovary. Pollen is deposited between the base of the beak and the head feathers. Both species are self-compatible and pollinator-dependent. In both Sinningia species, the combination of protandry, pollinator specificity, due to long corolla tubes that exclude the visitation of short-billed hummingbirds. The presence of particular flower features influence the occurrence of pollination by specific pollen vectors, such as hermit hummingbirds, in deterrence of illegitimate visitors (i.e. territorial hummingbirds), protection against vigorous foraging, and accurate placement of pollen on legitimate pollinators. In addition, the foraging of Phaethornis on flowers of Sinningia is independent of relative humidity and air temperature, whereas the main factor influencing hummingbird visits is the luminosity.