Geographical variation in the reproductive biology of widespread species often occurs at their distributional boundaries. We sought to determine whether such variation has occurred in an invasive orchid, Oeceoclades maculata, across its naturalized range. We compared its reproductive biology in a Brazilian population with that published for a population on the Caribbean island of Puerto Rico. In the state of São Paulo, O. maculata flowers between December and February, at the height of the rainy season. Similar fruit sets were observed in manual self (76%) and cross (70.4%) pollination treatments. The fruit set of plants protected from both pollinators and rainfall was 6.1%, whereas plants exposed only to rainfall had a fruit set of 41.4%, slightly less than the controls (48.3%). Like the Puerto Rico population, reproduction is primarily through rain-assisted autogamy, but unlike observations made on the island, outcrossing can eventually occur. We observed two butterfly species (Heliconius ethilla narcaea and Heliconius erato phyllis) pollinating O. maculata. Secretory epidermal cells and trichomes of the spur lumen produced 0.7 mL of 25% (sucrose equivalents) nectar per flower each morning, which was stored in a dilated basal portion of the spur and reabsorbed by the afternoon. Thus, geographical variation in reproductive biology exists across the broad invasive range of O. maculata.

The genus Vanilla is the most diverse in Vanilloideae, with ca 90 species distributed among tropical regions. Despite their economic importance, studies on pollination of Vanilla are very scarce and data on pollinators of species endemic to Brazil are lacking. Based on fieldwork and laboratory investigations, the floral biology of V. edwallii was studied. The pollinators and pollination process were recorded at the Serra do Japi reserve, state of São Paulo, southeastern Brazil, and the presence of floral reward was also investigated. Vanilla edwallii blooms in summer. The lateral inflorescences produce up to four pale green flowers. The white labellum is united to the base of the column forming a mentum. In the studied population V. edwallii is pollinated by Epicharis (Hoplepicharis) affinis, where the males exhibit a territorial behavior, defending flowers from other possible flower visitors. The pollen is deposited on the scutellum of bees when they abandon the flower. The mentum region is dry, suggesting no nectar production. The only secretory structures are osmophores dispersed on the inner surface of the lip responsible for production of a sweet fragrance, which together with color and morphology of flowers is related to bee attraction. The labellum is rich in mucilaginous cells, while the mucilaginous substance is retained inside the cells. The histochemical analysis also detected the presence of phenolic compounds and starch concentrated mainly at the adaxial surface of the lip and around the vascular bundles.

Many flowering plants present variable complex fragrances, which usually include different isomers of the same molecule. As fragrance is an essential cue for flower recognition by pollinators, we ask whether honey bees discriminate between floral-fragrance isomers in an appetitive context. We used the olfactory conditioning of the proboscis extension response, which allows training a restrained bee to an odor paired with sucrose solution. Bees were trained under an absolute (a single odorant rewarded) or a differential conditioning regime (a rewarded versus a non-rewarded odorant) using four different pairs of isomers. One hour after training, discrimination and generalization between pairs of isomers were tested. Bees trained under absolute conditioning exhibited high generalization between isomers and discriminated only one out of four isomer pairs; after differential conditioning, they learned to differentiate between two out of four pairs of isomers but in all cases generalization responses to the non-rewarding isomer remained high. Adding an aversive taste to the non-rewarded isomer facilitated discrimination of isomers that otherwise seemed non-discriminable but generalization remained high. Although honey bees discriminated isomers under certain conditions, they achieved the task with difficulty and tended to generalize between them, thus showing that these molecules were perceptually similar to them. We conclude that the presence of isomers within floral fragrances might not necessarily contribute to a dramatic extent to floral odor diversity.