Pollinator visitation patterns are influenced by floral volatile profiles

Abstract

Pollinators seek high quality nectar and pollen rewards critical for their growth and reproduction. Volatile emissions from inflorescences may signal plant health and floral resource quality to these flower-visiting insects. To understand the relationship between floral volatile emission and pollinator preference in a field setting, we conducted a replicated garden experiment consisting of 18 native perennial species from three different plant families with varying nutritional resource quality. We collected flower-visiting insects and floral volatile emissions over two field seasons, detecting over 60 volatile compounds and over 150 insect species. We collated trait data of visiting insects (bee or non-bee, body size, degree of sociality, nesting behavior, and whether the visitor was non-native) and evaluated interactions between these traits and volatile composition. Among the insect traits, bees and larger visitors had negative associations with sesquiterpenes, while in contrast visitors with complex nesting behaviors and social insects had positive associations. When comparing plant traits with bee traits, bee visitors had negative associations with purple inflorescences and larger insects and social insects both had positive associations with yellow inflorescences. We tested for direct associations between volatile class and insect taxa and found that sesquiterpenes had a strong positive relationship with hoverfly presence. This work demonstrates the complexity of floral volatiles as signals for pollinating insects and how floral scent composition allows individual compounds to act synergistically or antagonistically. These results can help us to better understand pollinator preferences and visitation patterns in the broad context of chemical ecology.