DIVERSITY OF FLOWER VISITORS AND THEIR ROLE FOR POLLINATION IN THE ORNITHOPHILOUS BROMELIAD VRIESEA FRIBURGENSIS IN TWO DIFFERENT HABITATS IN SOUTHERN BRAZIL

Abstract

In order to analyze species richness of flower visitors to the bromeliad Vriesea. friburgensis, and to relate the visitor spectrum to resource availability and differences in habitat, we studied its floral biology in two habitat types: dune vegeta- tion and secondary Atlantic rain forest on Santa Catarina Island, southern Brazil. Flowering extends from October to February, the anthesis is diurnal. We found the reproductive system to be partially autogamous without the possibility of intra-floral selfing. Therefore the bromeliad is pollinator-dependent, but the flowers do not need to be cross-pollinated. Mean nectar sugar concentration was 20.7% with a high sucrose proportion. Flowers secreted 73.9 μl nectar per day. Although the flowers show ornithophilous features like tubular and scentless flowers and higher energetic nectar in the morning hours, besides two hummingbird species we recorded 28 species of insects and spiders also associated with the flowers of V. friburgensis. Species richness of flower visitors was higher in restinga than in secondary forest. In both habitat types hummingbirds and bees were the most frequent visitor groups, but whereas hummingbirds were the most frequent animals visiting flowers in secondary forest, followed by bees, the opposite was the case in the restinga habitats. Because V. friburgensis is partially autogamous, small bees might also be pollinators, transferring self-pollen. Thus, there is redun- dancy in the pollination service provided by birds and bees, leading to a high probability of successful reproduction in this bromeliad species. Accepted 31 January 2011.