Many plant species possess flowers that are assumed to be adapted for certain types of pollinators, while these pollinators are assumed to restrict foraging to plant species with flowers that possess certain traits. Plant species that are assumed to be adaptive towards a particular pollinator type may possess floral traits that increase the plant’s attractiveness to these pollinators and/or facilitate reward extraction by these pollinators. Nicotiana section Alatae consists of several species with variation in visual, olfactory, and gustatory cues that are correlated to their predominant pollinators (hawkmoths, small moths, and hummingbirds). This study investigated whether these phenotypic differences resulted in variation in attractiveness or ease of obtaining nectar for hawkmoth pollinators. Individual, naïve hawkmoths (Manduca sexta) were tested using double-bout assays with single plants. Focal assays presented hawkmoths with one of six different Nicotiana species in the first bout, followed by a second bout with the hawkmoth-pollinated species, N. alata, to confirm motivation to feed. Responsiveness and latency were behavioral variables scored to determine the attractiveness of the species to the hawkmoth. Discovery time and success rate were variables scored to assess the degree of difficulty associated with the hawkmoth obtaining the nectar reward (extent of facilitation).
Results/Conclusions
During initial bouts, hawkmoths were always responsive (attempted to forage) with the hawkmoth-pollinated N. alata. All other Nicotiana species elicited foraging attempts from a percentage of hawkmoths significantly less than that for N. alata, with variation in responsiveness among these other species. Hawkmoths were more responsive to the small moth-pollinated, N. bonariensis, and the hummingbird-pollinated, N. mutabilis, than the other hummingbird-pollinated species, N. forgetiana and N. langsdorffii, and almost completely unresponsive to the putative new species, “Rastroensis” (hummingbird-pollinated). Similar patterns were found for latency. Therefore, floral traits do appear to affect the attractiveness of the species to naïve hawkmoths. Video analysis is still underway to assess the degree to which floral traits may facilitate foraging by hawkmoths. These results can have important implications for the evolution of these and other species.