Estudo comparativo de flores polinizadas por beija-flores em tres comunidades da Mata Atlantica no sudeste do Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

This study brings an analysis of information concerning the relationships between a group of ornitophilous flowers and hummingbirds, carried out at three rainforest sites in the state of São Paulo, the sites are Caraguatatuba, a coastallowland rainforest, and two highiand rainforests: Cunha and Campos do Jordão. The study has its main focus on floristic composition, phenology, floral biology, and diversity of floral attributes of ornitophilous native flowers. Additionally, this study assesses the composition, occurrence and behaviour of hummingbirds. The motivation for the gathering and study of such comprehensive information is the improvement of knowledge on pollination by hummingbirds and the complementation of otherwise fragmented data on flower hummingbird interactions in rainforests of southeastern Brazil. The number of native species pollinated by hummingbirds found in the three communities is eighty two, distributed in twenty four families and forty four genera. Few ornitophilous species are represented in each family or genera, except for Bromeliaceae that represents 30% of the ornitophilous species. In this study, the greatest richness of species occurs in the highiand forests of Cunha, but there is evidence that lowland forests might have greater richness of species, due to the presence of a large number of Bromeliaceae in these lowland areas. The computation of the Jaccard index for these three sitesshows similarity between the highland communities of Cunha (Serra do Mar) and Campos do Jordão (Serra da Mantiqueira); furthermore, the similarity index shows that the highiand sites differ in floristic composition from the lowland site of Caraguatatuba (Serra do Mar). There is a predominance of epiphyte habits among ornitophilous species; such tendency to epiphytism is strongly encouraged by the richness of species of Bromeliaceae and Generiaceae in this florestal formations. The sequential and continuous phenologic pattern predominates for the omitophilous community of the three sites, but the flowering patterns of the species located at Serra do Mar are not subject to sazonality. In the Serra da Mantiqueira the omitophilous species seem to follow the climatic sazonality of the region. In addition to Bromeliaceae, nine other families represent the main source of nectar for hummingbirds along the year; five families occur in coastal lowland sites (Costaceae, Fabaceae, Heliconiaceae, Lobeliaceae, and Marcgraviaceae) and four families are found in highland sites (F abaceae, Lobeliaceae, Malvaceae, and Onagraceae). The average sugar concentration and volume of nectar for ornitophilous flowers is 23.3% and 19.5%, respectively. The lowland rainforest of Caraguatatuba exhibits slightly larger concentrations of sugar in the nectar than those measured for the highland forests. The greater concentration is probably a consequence of greater richness of species of Bromeliaceae which produce thicker nectar. The studies carried out so far do not show any significant differences between the sugar concentration and volume of nectar of the lowland and highland forests; in contrast to what has been reported for other neotropical regions. Such difference can be linked to the importance of Trochilinae and Phaethorninae as pollinators of highland and lowland flowers, respectively. This absence of qualitative and quantitative differences in nectar can be related to the influence of Phaethominae in the three communities studied. There are several floral types among the ornitophilous flowers of the three communities, the majority has tubular flowers, a consequence of 60% of ornitophilous flowers belonging to the subclass Asteridae. The diversity of corolla shapes and sizes in ornitophilous flowers plays an important role in determining where polen is deposited on the body of the pollinator. Most of the pollen is deposited on the bill of the hummingbird; this fact is related to the predominance of tubular flowers and to the position of the anters inside the tube. The definition of floral subgroups for each ornitophilous community is a function of the frequency of visits to flowers by hummingbirds. Two floral subgroups have been established for the lowland forest, one is associated to Ramphodon naevius, and the other is associated to Phaetornis ruber and the female of Thalurania glaucopis; four floral subgroups have been defined for the highland forests, each one is associated to hummingbirds regularly found in these forests sistes: Phaethornis eurynome, Leucochloris albicollis, Clytolaema rubricauda, and Stephanoxis lalandi. The largest floral subgroup is associated to R. naevius that dominates resources in lowland sites and the smallest subgroup is linked to C. rubricauda that exploits rich floral resources of highland sites. P. eurynome and L. albicollis show a considerable overlapping in their use of floral resources, even though P. eurynome is the exclusive pollinator of some species. The seven hummingbird species found in the studied sites perform five functions in the community: generalist, territorial, low-reward trapliner, high-reward trapliner, and territory parasite. The communities studied can be considered rich in number of ornitophilous species, and moderately rich in hummingbirds, specially in the highland communities. The Phaethominae can be considered the main pollinator in theses communities, having a participation of approximately 80% as pollinator of omitophilous tlowers in both lowland and highland forests. The overlapping in resource use exhibited by hummingbirds Phaethominae and Trochilinae can be advantageous to flowers as it translates in a redundancy of pollinators, that is, pollination is potentially guaranteed even when one of them is absent

ASSUNTO(S)

fenologia polinização mata atlantica flores beija-flor

ACESSO AO ARTIGO

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