Legitimate pollination of the tristylous flowers of Eichhornia azurea (Pontederiaceae) by Ancyloscelis gigas bees (Anthophoridae, Apoidea)

Eichhornia azurea is a tristylous species of Pontederiaceae. Moderate self- incompatibility accompanies the floral heteromorphism of this species. Eich hornia azurea is almost exclusively visited by one bra species, Ancylosceli s gigas (anthophoridae), in South Brazil. This species has an extremely lon g proboscis covered with recurved hairs. Bees use these hairs to collect po llen from the anthers placed inside the narrow perianth tube of E. azurea. Analyses of the pollen load of A. gigas females show that they are flower c onstant and carry pollen from all three anther levels. The behavior of A. g igas and its proboscis morphology make this bee species narrowly adapted an d an effective pollinator for facilitating legitimate pollination of E. azu rea flowers in southern Brazil.