Biologia da polinização da especie arborea Citharexylum myrianthum Cham. (Verbenaceae), polinizadores e utilização do recurso floral pelos visitantes

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

Citharexylum myrianthum is a tree, typically found in the Atlantic Rain Forest and gallery forests, in early successional stages and it is a very important component in the regeneration of degraded areas, ranging from south Bahia to Rio Grande do Sul. We studied the phenology of this species, its floral biology, pollinators, and visitors in Campinas and in Picinguaba, SP, and also in Porto Alegre, RS. Citharexylum myrianthum flowers from October to December, bearing great quantity of flowers per plant per day. The tubulous flowers are white, sweet scented and occur in racemous inflorescences. AlI plants have flowers with a gynoecium and an androecium, however, they are functionally dioecious. The male plants are in flower some days before the female ones. In both flower types, the gynoecium is receptive before anthesis until the fall of the flower. The flowers open between 0400 p.m. and 0630 p.m., and they may last until the day after by 0300 p.m.. The nectar production begins in the dusk and stops by the early morning. The accumulated nectar volume made in bagged flowers is about 10,5-15 J..Ll and its concentration is 15%. We made 71 hours of nocturnal observation, besides census at each 10 min to quantify the sphingid visits to the plants along the night, during six nights. Sphingids are considered to be the major group of pollinators, visiting flowers at dusk and at nighí. They are more frequently observed on male plants at about 1000 p.m. and in the female ones by 0300 a.m.. The low fruit set under natural conditions compared with the very high fruit production after hand-pollination suggests that these pollinators are a limiting resource to the plants. To determine the diurna! visitors activity we made three observation periods (0600-0700, 0800-0900 and 1000-1100 a.m.), making 95 hours of observations. To locate the visits to the flowers, the canopy was divided into three floors and each one into areas of 3x3. Eight species of hummingbirds in Campinas and seven in Picinguaba, among residents and migrants, used the nectar resource of C. myrianthum, displaying agonistic interactions and making use of the flowers in different ways in space and time. Species of hummingbirds with greater body mass and more aggressive were responsible for the majority of the flowers visited, excluding coespecifics and other species from the region of the canopy with more resource concentration during a certain period of time. Among other visitors, Coereba flaveola (Coerebidae) and Thraupis sayaca (Emberezidae) were frequent in Campinas and in Picinguaba, robbing nectar and even destroying the flowers. Diurna! insects were more common in Campinas and Trigona spinipes and Po/istes sp. could be seen making holes on the corolla to remove the nectar of C. myrianthum. By the end of the morning, butterflies, mainly Papilio anchisiades, visited the flowers of C. myrianthum and they may be occasional pollinators

ASSUNTO(S)

plantas - reprodução polinização beija-flor mata ciliar

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