Interaction network and the relationships between bromeliads and hummingbirds in an area of secondary Atlantic rain forest in southern Brazil

Abstract

The reciprocal importance of bromeliads and hummingbirds has been proposed for many years, even suggesting coevolution between these two groups. Nevertheless, data are lacking that allow a better test of the relationships involved. Here we investigate the relationship between bromeliads and hummingbirds in an area of secondary Atlantic rain forest in southern Brazil. The study examined the interactions among 12 species of bromeliad and 10 of hummingbird at Reserva Natural Salto Morato, Paraná state. The number of flowering species of bromeliad and the species richness and abundance of hummingbirds were quantified monthly between November 2004 and October 2005. Focal observations on each bromeliad species were made to determine the hummingbird visitors. Neither species richness nor abundance of hummingbirds were related to bromeliad phenology. Together with the monthly variation in visit frequency by a given pollinator to a given plant, these factors indicate a generalization in the use of bromeliads by hummingbirds and argue against tight coevolution. Ramphodon naevius and Thalurania glaucopis were the main pollinators in the community. Aechmea nudicaulis was the most generalist bromeliad species. The generalist species interacted with other generalists or with asymmetric specialists and there was no specialist–specialist interaction. This produced a strongly organized and nested matrix of interactions. This nestedness is similar to other plant-pollinators networks, supporting the hypothesis that the evolutionary relationship between bromeliads and hummingbirds is no stronger than that of other pollination networks.