Abstract: Pollinators seeks high quality nectar and pollen rewards which are critical for growth and reproduction. Specifically, the emissions from inflorescences may act as a signal of plant health and resource quality to visiting pollinators. To understand the relationship between floral volatile emission and pollinator preference, we conducted a replicated garden experiment consisting of 17 native perennial species from three different plant families (Asteraceae, Lamiaceae, Fabaceae) with varying pollen and nectar nutritional quality. We recorded insect visitation to inflorescences of these plant species over two field seasons. We also collected volatile emissions with dynamic headspace sampling and solid phase microextraction (SPME) and analyzed them with gas chromatography-mass spectrometry (GC-MS). We detected over 70 volatile compounds from several chemical classes and over 150 insect species from multiple orders (Hymenoptera, Diptera, Coleoptera, Lepidoptera). We collated trait data (size, sociality, functional group, nesting behavior, and whether the insect is non-native) on the insect visitor species that comprised 95% of the abundance in the experiment and evaluated interactions between insect traits and volatile composition (categorized by chemical class). Among the insect traits, body size exhibited both the highest magnitude and greatest number of significant relationships with volatile compounds. For example, body size had a negative association with the compound cubebene and a positive association with amorphene. Among the volatile compounds, amorphene had both the highest magnitude and largest number of associations with the measured insect traits, and correlated positively with bee visitation and nesting complexity, and negatively with sociality and non-native visitors. When we tested for direct associations between insect visitor species and volatile compounds, we found insect visitors had more positive interactions with sesquiterpenes than any other chemical class. Isopulegone had the highest magnitude and greatest number of overall significant relationships with insect visitors, while the bee family Halictidae had the greatest number of significant relationships of the insect visitors. Bergamotene was the compound with the greatest positive magnitude with insect visitation. These results reflect the complexity of how insect visitors interact with floral volatile emissions while foraging and may help us to better understand pollinator preferences and visitation patterns.
