Working Towards a Holistic View on Flower Traits— How Floral Scents Mediate Plant–Animal Interactions in Concert with Other Floral Characters

Abstract

Flowers are complex structures, synchronously displaying both olfactory and visual signals/cues in the context of a particular floral morphology, that also vary in resource quantity and quality. Despite or possibly because of this complexity, many studies focus on a single or few traits rather than studying floral phenotypes in a more integrated fashion. However, each of these distinct trait classes (signals/cues, morphology and resources) mediates interactions with floral visitors, demanding a more holistic view of flowers. In our review, we integrate floral scents into the broader context of the whole-flower phenotype. We discuss the functions of scent bouquets, colouration, morphology and rewards in flower–visitor interactions from an ecological and evolutionary perspective in isolation and taken together. Studies demonstrate that floral scent bouquets can act additively or synergistically with other modalities, and that their effects on flower visitors are context-dependent. We also present field study results showing that reward levels modulate dose-dependent responses to volatiles by honeybees. To motivate studies examining complex floral phenotypes, we outline statistical approaches suited to deal with the complex multivariate datasets generated by these studies. We conclude with a discussion on why flowers display multimodal traits and suggest future research efforts. Our aim is to foster a fresh view on integrated floral phenotypes and stimulate studies exploring the combined effects of olfactory, visual, morphological and nutritional traits on flower–animal interactions.