Inter‐kingdom signaling — symbiotic yeasts produce semiochemicals that attract their yellowjacket hosts

In recent studies, the yeast speciesHanseniaspora uvarumandLachancea thermotoleranswere isolated from the digestive tract of four North American yellowjacket species (Hymenoptera: Vespidae), and attraction of yellowjackets to brewer's yeast,Saccharomyces cerevisiae(all Saccharomycetaceae), growing on fruit powder was demonstrated. We tested the hypothesis thatVespulaspp. are attracted to cultures ofH. uvarumandL. thermotoleransand their respective volatiles. In field experiments, we found thatH. uvarumandL. thermotoleransare attractive to three species of yellowjacket, but only when grown on grape juice‐infused yeast peptone dextrose (YPD) agar. Using gas chromatography‐mass spectrometry, we analyzed the headspace volatiles produced by these yeasts, and field tested an 18‐component yeast synthetic semiochemical blend. This synthetic blend attracted western yellowjackets,Vespula pensylvanica(Saussure), but no other yellowjacket species. Acetic acid or ethanol added to the synthetic blend at biologically relevant doses either had no effect or significantly lowered trap captures. Our results demonstrate that yeast symbionts isolated from the digestive tract of yellowjackets are attractive to their hosts. Further research is needed to identify the volatiles mediating attraction of species other thanV. pensylvanicato the yeast cultures.