title: Flower Visitors of Campanula: Are Oligoleges More Sensitive to Host-Specific Floral Scents Than Polyleges?
abstract: The pollen diet provided by adult bees to their offspring varies immensely. While some species collect pollen on several plants irrespective of their phylogenetic relatedness (polyleges), others collect only on plants within a genus or family (oligoleges). Floral scents play a central role in bee-plant interactions. To locate flowers, polyleges are assumed to rely on compounds commonly found as floral scent constituents, whereas oligoleges rely on unusual compounds to recognize host flowers unambiguously. Campanula flowers are visited by both polylectic and oligolectic species, and their scent bouquets consist of common and unusual (e.g., spiroacetals) volatiles. In a comparative approach, we performed electroantennographic analyses to investigate the antennal responses of three polyleges and three oligoleges to three common volatiles and four spiroacetals. We hypothesized that: 1) oligoleges and polyleges should respond similarly to common flower volatiles, and 2) Campanula oligoleges should be more sensitive to spiroacetals than are polyleges. In corroboration, we found that antennal sensitivity to common volatiles was similar among bees irrespective of pollen diet, whereas oligoleges of Campanula were more sensitive to spiroacetals than polyleges. Newly emerged bees of the Campanula oligolege Chelostoma rapunculi rely on spiroacetals for recognizing host-flowers, and our results suggest that this might also be true for other Campanula oligoleges, since Chelostoma campanularum and Hoplitis mitis also were able to perceive these specific volatiles at very low concentrations. Together, our results provide interesting insights into the significance of olfactory adaptations in oligolectic and polylectic bee species.
authors.affiliation: Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Brandt
authors.affiliation: Department of Ecology & Evolution, University of Salzburg, Salzburg, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Dötterl
authors.affiliation: Institut für Organische Chemie, University of Hamburg, 20146, Hamburg, Germany.
authors.forename: Wittko
authors.initials: W
authors.lastname: Francke
authors.affiliation: Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Ayasse
authors.affiliation: Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany. miletpinheiro@hotmail.com.|Departamento de Botânica, Universidade Federal de Pernambuco, Recife, Brazil. miletpinheiro@hotmail.com.
authors.forename: Paulo
authors.initials: P
authors.lastname: Milet-Pinheiro
mesh_terms: D000080:Acetals / Q000032:analysis; D000818:Animals; D057506:Arthropod Antennae / Q000502:physiology; D001516:Bees / Q000502:physiology*; D029422:Campanulaceae; D055724:Electrophysiological Phenomena; D005260:Female; D035264:Flowers / Q000737:chemistry*; D009812:Odorants / Q000032:analysis*; D054817:Pollination; D013045:Species Specificity; D013141:Spiro Compounds / Q000032:analysis
chemical_list: D000080:Acetals; D013141:Spiro Compounds
keywords: Electroantennography (EAG); Floral scents; Olfactory receptors; Oligolecty; Polylecty; Spiroacetals