Nectar or perfume as reward? Investigating the pollination and chemical ecology of the bromeliad <i>Cryptanthus bahianus</i>

Perfume flowers provide chemicals as a resource for specialized pollinators, that is, male euglossine bees. This system has been recorded in at least 15 families of Neotropical Angiosperms, including species of the bromeliad genus Cryptanthus. Here, we investigated the pollination and chemical ecology of Cryptanthus bahianus, a potential perfume flower species with an unknown pollination mechanism, emphasizing the possible role of floral signals in pollinator attraction. In a population of C. bahianus situated in NE Brazil, we described the anthesis, determined the breeding system, measured the volume and concentration of nectar, and characterized the main floral cues, such as morphology, colour, and floral scents. Additionally, we investigated the interactions between flowers and their visitors. C. bahianus is an andromonoecious species with diurnal anthesis, beginning at 05:00 h, when nectar is already available. Its white tubular flowers secrete 9 ± 2.8 μL of nectar, with a mean concentration of 18.7% ± 6.96%. The major compounds in the floral scent were benzyl alcohol, (Z)- and (E)-3-methyl-4-decenoic acid, which together accounted for 95.49% of the total bouquet. Floral visitors included male and female euglossine bees, seeking only nectar. C. bahianus offers nectar and, eventually, pollen as floral rewards, contrary to expectations related to the pattern found in three other species of this genus, which have perfume flowers. Chemical analyses of the floral scent of C. bahianus did not reveal the presence of copalol, a semivolatile diterpene produced by flowers of C. burle-maxii and sought by its male euglossine pollinators. The fact that C. bahianus occupies a basal position in the Cryptanthus phylogeny suggests that nectar is a plesiomorphic trait in the genus and that perfume flowers might have evolved from nectar flowers.