From signals to fitness: Behavioral responses to floral signals of nectar quality affect hawkmoth fitness

Abstract

Interactions between insect pollinators and the flowers they visit are most commonly studied from a pollen-transfer perspective. However, these interactions are examples of complex interspecies communication and signaling interactions in which floral allocation, as well as individual pollinator perception and behavior can strongly influence the outcome. This dissertation focuses on the dynamics influencing floral investment in attracting pollinators, pollinator preferences for floral rewards of variable quality, and the resulting effects on the lifetime fitness of individual pollinators. I constructed a game theory model of a plant’s individual allocation to floral attractiveness, incorporating parameters accounting for plant biology, inter-plant competition for pollinator services, and pollinator abundance and perceptual ability. In addition to plant life history parameters, this model identified pollinator behavior and perception as an influential factor in determining allocation to floral attractiveness. Subsequently, I conducted experiments utilizing the specialized, hawkmoth-pollinated evening primrose Oenothera flava. Using this pollination system I demonstrated that naïve foraging hawkmoths exhibit innate preferences for floral nectars containing amino acids, and are able to learn and associate variation in floral signals with varying nectar quality. Thus, an experienced forager is able to discriminate between co-flowering plants and forage preferentially for nectars of higher quality. Finally, by tracking hawkmoth lifetime fitness I was able to show that adult foraging success and nectar quality impact hawkmoth mate choice, longevity, and lifetime fitness. Collectively, these results demonstrate that pollinator perception and behavior are likely to have substantial influence on a plant’s allocation to floral signals. Further, foraging pollinators learn variation in these signals and forage preferentially on higher quality plants in order to enhance individual fitness.