Biologia reprodutiva de L. leucocephala (Lam.) R. de Wit (Fabaceae: Mimosoideae): sucesso de uma espécie invasora

Abstract

The species Leucaena leucocephala (Lam.) R. de Wit., known as leucaena, is originally from Central America. It has been considered a pioneer with high densities of individuals in its populations that could prevent the development of native species. The present study aims to understand the reproductive biology of L. leucocephala, synthetizing information about its reproductive success. The study was conducted in Trindade, central Brazil, from July to November 2012. All areas contained specimens in bloom. We selected four study areas containing populations of leucaena with at least six individuals with flowering. Observations were made of floral visitors and we did tests of first, second and third visit, and cross-pollination between plants, self-pollination and control group (without human intervention). There was a predominance of Apis mellifera and Trigona spinips as flower visitors in these areas. The flowers undergo senescence at the end of the day, however, there is a decrease in flower visiting by insects after 10 am. We found 342 visitors belonging to 12 insect species. After assessing the number of visits of pollinators and their influence on fruit production, we found that the number of visits of the main pollinator (A. mellifera) does not influence the production of fruits, showing the efficiency of this bee in its first visit to flowers. Leucaena leucocephala combines several attributes to be considered an invasive species, such as the efficient action of generalist pollinators as Apis mellifera, being able to produce considerable amounts of fruits and seeds that contribute to the potential dispersal and reproductive success of the plant.