Sweet to arrive, fermented to fly: flower-insect interactions in a Mexican dry forest population of Annona macroprophyllata (Annonaceae)

Flower scents are crucial for attracting pollinators to Annonaceae flowers. Pollinators are likely drawn exclusively to female flowers. Since pollinators remain inside the pollination chamber throughout anthesis in several species, it is believed that the aroma during the male phase does not attract pollinators and may even repel them. However, few studies have characterised the scents of Annonaceae species flowers during both the male and female phases, so this hypothesis has not been comprehensively evaluated. Here we characterise the reproductive ecology of Annona macroprophyllata, including individual- and flower-level phenology, mutualistic and non-pollinating interactions, and floral scent emissions. Our results showed that Annona macroprophyllata has receptive flowers at night, with the entire extent of reproductive activity restricted to an 8 hours-period. Female and male flowers are synchronous with differences in the proportion of flowers depending on the nighttime. Low diversity and abundance of floral visitors were observed. Four guilds were distinguished as pollinators, florivores, insect predators and random or non-specific visitors. Pollinators were insects (Nitulidae) that entered the pollination chamber during the female phase and remained inside the flower throughout anthesis. The comparison of floral scent diversity among flower phases showed that scent composition differs between the phases of A. macroprophyllata flowers. The scent of the female flower mimics the sweet smell of fruit, which usually attracts Nitulid beetles. In contrast, the fermented odors of the male phase seem to repel them, contributing to their release or ensuring that they visit only female flowers. This study reveals an attraction-repulsion pollinator system in Annona macroprophyllata, which could be a common floral attribute within the Annonaceae family.