Sistemas reprodutivos e polinização em espécies simpátricas de Erythroxylum P. Br. (Erythroxylaceae) do Brasil

Abstract

(Breeding systems and pollination of sympatric Erythroxylum P.Br. (Erythroxylaceae) from Brazil). The breeding systems and pollination of Erythroxylum campestre St. Hil., E. suberosum St. Hil. and E. tortuosum Mart. were investigated on the Fazenda Água Limpa, UnB, Brasília, DF. These species are sympatric, and are commonly found in open cerrados where they flower synchronously for about four months. They are distylic, that is, they have flowers with long styles (pin) as well as with short ones (thrum), both of which possessing stamens of a corresponding height. Flowers of the three species are similar, being small, sweetscented, creamish, and diurnal, as well as nectar producers (sugar concentration about 20.2%), and lasting for only one day. Artificial pollination revealed that E. suberosum and E. tortuosum are self-incompatible and that fruits were obtained only by legitimate cross-pollination. E. campestre is partially self-compatible. In all species the number of fruits resulting by natural pollination was higher than that by the artificial means. Except for E. campestre, fluorescence microscopy studies revealed that pollen tubes in pin flowers from self-crosses were arrested in the styles and in the thrum flowers at the stigmas. Flowers of the three Erythroxylum were indistinctly visited by 14 wasp species, 14 bee species and two diptera species. Brachygastra, Polistes, Polybia and Pepsis wasps were considered effective pollinators, based on efficiency in contacting the stigmas, while Trigona spinipes and Apis mellifera were considered occasional pollinators.