False Advertising with Fermented Scents: Floral Mimicry in Pawpaw (Asimina triloba: Annonaceae) Pollination

Premise of research. Floral mimicry of nonfloral substrates frequently involves mimicry of microbial volatile blends, tapping into the chemical ecology of diverse saprophagous insects. We investigate pollination of Asimina triloba, a temperate woody species with yeasty-smelling maroon flowers that bloom in early spring and putatively mimic fermenting substrates. Specifically, we identify likely pollinators and present evidence of floral mimicry of fermentation by investigating a range of fermenting substrates in the local environment. Methodology. To test floral mimicry, we characterize naturally occurring fermenting substrates that co-occur with blooming A. triloba. We compare odor chemistry of substrates to floral scent and identify insect species captured from flowers and visiting fermenting substrates. Pivotal results. Substrates sharing volatile chemical overlap with floral scent of A. triloba include sap flows, decaying floral tissues, fermenting mulberries, and frugivore dung. Several substrates shared major components of the floral scent chemistry, including acetoin, 2,3-butanediol, and ethanol. True flies (Diptera) represent a majority of insects collected from within flowers and upon substrates. Flies collected from flowers represent 20 species from nine families. A majority of species collected from flowers were also collected from substrates. Conclusions. These results all support the hypothesis of floral mimicry of fermenting substrates as a pollination strategy for A. triloba. We emphasize the importance of understanding the ecology of diverse pollinating taxa and examining diverse potential models when investigating floral mimicry.