Innate preferences of Eristalis tenax L. (Syrphidae) for flower colour, size and symmetry are more intricate than the simple additive model

Abstract

Abstract Plants have evolved complex flowers that differ in visual traits such as colour, size and shape, to attract pollinators. However, pollinators seem to respond differently to individual traits. Our objective was to unravel the effect of individual traits and their interplay in forming pollinator preferences. We measured the preferences of naive drone flies, Eristalis tenax (Syrphidae), for artificial flowers differing in colour, size and flower symmetry, in controlled conditions to untangle the effects of individual traits on pollinator behaviour. Eristalis tenax showed the highest selectivity for colour, followed by size, and only moderate selectivity in relationship to flower symmetry. Flower colour interacted with flower size, in that yellow colour was generally preferred, particularly when the flowers were large in comparison to other forms. Our results suggest that preferences for flower traits are structured, which might suggest that there have been different evolutionary pressures on individual floral traits.