THE STUDY OF INTERACTIONS BETWEEN BIRDS AND FLOWERS IN THE NEOTROPICS: A MATTER OF POINT OF VIEW
Authors: Márcia A. Rocca and Marlies Sazima
Abstract: Birds are among the main components for plant reproduction in tropical ecosystems, with hummingbirds being the most important vertebrate pollinators in the Neotropics. Flower-visiting birds of another groups (the perching birds) are often considered as parasites of the flower-hummingbird relationships. These birds do not present a high degree of specialization for nectarivory, although nectar should be a very important component of the diet of some groups. Birds usually also visit non-ornithophilous flowers, as they look for resources in flowers adapted to pollination by other animals as well. However, very few studies have focused on non-ornithophilous flowers, which means looking at the whole group of species visited by birds, from the bird’s point of view— the resource approach. While visiting non-ornithophilous flowers, birds (usually hummingbirds) may act merely like robbers, thieves or even copollinators. Therefore, when the aim of the study is pollination, one should not only look for ornithophilous flowers, but also for other possible bird pollinated species, from the flower’s point of view—the pollination approach. Studies focusing on this last approach are even scarcer at the community level. It is important to realize that the set of ornithophilous species are inside the wider set of pollinated species by birds, and this one is contained inside the set of visited species by birds. Studies that only pick up ornithophilous species from a community are not focussing on pollinated species by birds, but rather on a subset of that. Another problem of point of view is that most studies in the Neotropics are ground based, which may reduce sampling of canopy species information. Observation positions within the canopy greatly enhance this kind of study and should be used more often. As flowers pollinated by perching birds may be more common in the canopies of Neotropical forests, perching bird flowers and their visitors and pollinators are underestimated in communities sampled only from the ground, which means that the majority of the studies on bird-flower interactions in Neotropical forests present good lists of bird and plant species, but very incomplete interaction networks. After putting together these different approaches to study the bird-flower interaction network, we could maybe build—with the help of other animal-flower networks—a picture of a combined model of nested compartments to the whole community, connecting all animal-flower networks by interactions of co-pollination or just visits, reinforcing the idea of communities displaying high connectance.
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