Biologia de Polinizacion en una Comunidad Arbustiva Tropical de la Alta Guayana Venezolana

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Abstract
The pollination ecology of tropical shrubland was studied in the Venezuelan Guayana Highlands. Most flowers are white or pink. Flower length is less than 0.5 cm for 45.5 percent of plant species (N = 55). The diameter has a similar distribution. Of the 62 visiting agents recorded on 55 plant species, 80.6 percent are pollinators and 19.4 percent are visitors only. Four families of bees are represented. Pollen is normally carried on only one location, frequently ventral, although it can be carried on the head or legs. Pollen transportation by wasps (four families) is frequently ventral on the body and legs. Lepidopterans (three families) carry pollen grains on their proboscis. Coleopterans are represented by two species of Scarabaeidae which transport pollen ventrally. They as well as the dipterans visit only one plant species. Three bird species visit plant species in the shrubland. Politmus milleri (Trochilidae) pollinates seven plant species and the pollen is transported on the beak and head feathers. At the community level, 56.2 percent of plant species are pollinated by hymenopterans, 10.9 percent by lepidopterans and 9.6 percent by dipterans, and one plant species (2.7%) by beetles. Bird-pollinated plants represent an important part of plants in the shrubland (12.3%). The anemophilous plants are 8.2 percent of total. From 148 species of visitors recorded on 49 zoophilous plant species, 37.6 percent of plant species are pollinated by medium size bees, 16.9 percent by large bees and 10.1 percent by small bees. The small wasps pollinate 8.1 percent and large wasps pollinate 6.1 percent of plant species. Large flies visit 1.4 percent and small flies 2.7 percent of plant species.