SHAPE MATTERS: COROLLA CURVATURE IMPROVES NECTAR DISCOVERY IN THE HAWKMOTH MANDUCA SEXTA
Eric Octavio Campos, Thomas Daniel, Toby Bradshaw.
University of Washington, Seattle, WA.
Nectarivorous pollinators use a variety of floral cues while foraging. Flower morphology is recognized as a potentially important contributor to a pollinatorâ€™s ability to find and exploit the nectar source. However, it can be difficult to test hypotheses about the importance of whole-flower shape in pollinator foraging ability using either natural variation in floral form or traditional artificial flower construction techniques. We measured the effects of variation in whole-flower shape on pollinator foraging ability using the hawkmoth Manduca sexta and 3D-printed artificial flowers whose shapes were mathematically specified with 4 shape parameters. In dimorphic arrays containing curved trumpet-shaped flowers and flat-disk flowers, hawkmoths visited trumpet-shaped and flat-disk flowers with equal frequency but were able to find the nectar source in significantly more trumpet-shaped flowers regardless of nectary aperture size. Interestingly, trumpet-shaped flowers needed to deviate only slightly from the flat-disk morphotype in order to significantly increase hawkmoth foraging ability. Our study shows that whole-flower 3D shapes, particularly corolla curvature, have the potential to act as a mechanical nectar guides for M. sexta, further implicating direct flower-proboscis contact as an important contributor to success during flower handling in hawkmoths. Our approach of combining mathematical modeling with 3D-printing to construct precise and repeatable artificial flowers is novel and paves the way for previously impractical experiments regarding the importance of floral morphology in mediating plant-pollinator interactions.