The Putrescine Puzzle: How do Manduca sexta hawkmoths respond to scented nectar in Datura wrightii flowers?

Abstract

The unusual large amounts of a polyamine, putrescine, in the nectar of the Datura wrightii flower add complexity to the mutualistic interactions between the flower and its pollinator, Manduca sexta, acting as a potential modulator in the pollinator’s foraging behavior. However, whether this non-sugar metabolite acts as an attractant or a repellent in the floral nectar is not well understood. I performed an innate preference bioassay using the Datura nectar and a synthetic sugar solution to analyze the possible effects of putrescine on Manduca preference during foraging. Based on the assessment of the animal’s first choice, the frequency of visits per flower, and the final volume of nectar consumption measurements, this study failed to find any statistically significant difference in the moth’s preference between Datura nectar and the synthetic sugar solution. However, while the absence of behavioral changes may suggest the animal’s indifference towards the additional polyamines in the nectar, it remains possible that physiological or fecundity implications may arise from a long-term study.