Nectary and Nectar Features: Occurrence, Significance, and Trends in Bignoniaceae

Abstract

The variety of pollination strategies present in the Bignoniaceae makes the family ideal for comparative studies of the evolution of floral features. Six flower and nectar parameters were recorded from literature for 50 species (nectar concentration, volume per flower, and amount of sucrose, corolla length, and nectary size and stomata number). Comparisons were made between two pollinator guilds and two tribes. Significant differences were not detected between the tribes Tecomeae and Bignonieae (n= 21 and 16 species respectively). On the other hand, bee-pollinated species presented a higher nectar concentration and a lower nectar volume per flower than bird-pollinated species (n=29 and 8 species respectively). Results showed that some nectar features are correlated with the different pollinator guilds and may indicate nectar adaptations by flowers to their pollinators. Floral structural traits seem to be more conservative than nectar features because the lack of significant differences between tribes and pollinator guilds at both the species and the genus level. These patterns suggest that pollinators would be involved in primary changes on nectar traits and later, in a second evolutionary step, on structural floral modifications.