Krameria flower volatiles as potential signals for oil-collecting bees

BALBUENA, MARÍA SOL; BUCHMANN, STEPHEN L.; PAPAJ, DANIEL R.; RAGUSO, ROBERT A

Congreso; VII ALAEQ; 2023

Oil-producing flowers are pollinated by specialized bees that collect oils as a reward. The oil is secreted in floral glands called elaiophores and it is used by female bees for nest construction or combined with nectar and pollen as provisions for larval brood cells. Some plants that offer acetylated glycerols as floral oils emit diacetin, a volatile by-product of oil metabolism, which oil-collecting bees use as an index signal communicating the presence of floral oil. However, flowers of the genus Krameria (Krameriaceae) produce oils that lack acetylated glycerols, making them unlikely to emit diacetin as a bee attractant. Given this, it is unclear if there is another compound that acts as a signal (conventional or index) for oil-collecting Centris bees to recognize Krameria flowers. Here, we studied the volatile organic compounds in the headspace of K. bicolor and K. erecta whole flowers and dissected floral parts using solid-phase microextraction. Through gas chromatography-mass spectrometry, we identified 26 floral volatiles for K. bicolor and 45 for K. erecta. Diacetin was not detected; however, -ionone was uniquely present in dissected elaiophores of K. bicolor, as well as the larval cells and provisions from its oil-bee pollinator, Centris cockerelli. Instead, the elaiophores of K. erecta, which are not visited by C. cockerelli, produced a blend of anise-related oxygenated aromatics not found in the elaiophores of K. bicolor. Thus, -ionone emerges as a potential candidate for an index signal for C. cockerelli. Our findings also suggest that -ionone could influence the foraging behavior of C. cockerelli due to larval imprinting on scented provisions or innate or learned preferences by foraging adults.