Ferne Kotlyar
PhD Candidate
University of Toronto Mississauga
PI: Prof. Helene Wagner
12 to 1 PM
IB 140 & Zoom
Title
Nectar Deposition on Stigma Drives Pollinator Recognition in a Hummingbird-Pollinated Plant
Abstract
Most species have evolved strategies to enhance genetic variation; in plants, this often involves promoting outcrossing. Morphological specialization is a major strategy to exclude ineffective pollinators and increase outcrossing, however, it does not fully account for observed outcrossing efficiency. We propose and test a novel mechanism by which plants may discriminate among pollinators. In the hummingbird-pollinated plant Heliconia tortuosa, nectar deposited on the stigma by specialized pollinators may enhance fruit set. First, we recorded 67 slow-motion videos of wild hummingbirds to confirm nectar could reasonably reach the stigma during visits. We then used nectar dye experiments to compare the likelihood of nectar deposition between specialized and generalist hummingbirds. We also tested whether simulated visits, using 3D printed hummingbird bill replicas combined with hand pollination, led to higher fruit set compared with hand pollination alone or hand pollination paired with nectar extraction. Finally, we broke down the simulated visits into two components: bill contact and nectar deposition. We evaluated these treatments separately to determine which factor most strongly contributed to fruit set. Nectar dye results (n = 55 flowers) showed that specialized pollinators are significantly more likely than generalists to deposit nectar on anthers and stigmas. Hand pollination experiments after simulated visits (n = 285 flowers) confirmed that nectar deposition on stigmas increases fruit set. A second pollination experiment (n = 468 flowers) demonstrated that simulated visits match natural fruit set, but neither bill contact, nor nectar deposition alone were sufficient. Our findings suggest that both nectar and bill contact with the stigma may be required for successful reproduction. Together, our results challenge the traditional view of nectar as merely a pollinator reward and underscore the importance of flower-bill trait matching in shaping plant-pollinator interactions and coevolution.
Visit Ferne's personal website to learn more about her, her research, and the company that she has co-founded, Heliconia Interactive!