Responses of butterflies to visual and olfactory signals of flowers of the bush lily Clivia miniata

Abstract

Experimental studies of the use of visual and olfactory cues by flower-visiting animals can shed light on the evolution of floral signalling traits. We examined the functional significance of floral traits in Clivia miniata (Amaryllidaceae). This forest lily with large orange trumpet-shaped flowers is pollinated mainly by swallowtail butterflies and belongs to a lineage with ancestral bird pollination. We used C. miniata flowers varying in colour, orientation and scent, and arrays of artificial flowers varying in colour, pattern, orientation, size, shape, and scent to assess foraging preferences of the butterflies that pollinate C. miniata. Butterflies preferred orange over yellow colour morphs of C. miniata and preferred red and orange model flowers over yellow ones. Orange models with a central yellow target ‘nectar guide’ were favoured over plain orange models. Butterflies also favoured large over small model flowers and preferred to alight on upward-facing flowers. Addition of scent compounds emitted by C. miniata flowers increased butterfly visitation to model and natural flowers. These results identify the importance of particular combinations of visual and olfactory signals for attraction of swallowtail butterflies and shed light on the floral modifications associated with a shift from bird to butterfly pollination.