Microbial odors mediate host finding in insect herbivores

Attraction of the fruit fly D. melanogaster to a blend of yeast volatiles with acetic acid as a main attractant compound (Becher et al. 2010, 2011) demonstrates the significance of ionotropic receptors (IRs) in Drosophila behavioral ecology. IRs have been discovered recently, they are tuned to acids and other microbial odors (Benton et al. 2009, Ai et al. 2010). With this in mind, we have investigated the role of yeasts for host finding and oviposition in other insect herbivores. We conclude that plant-yeast-insect interactions are more widespread than previously assumed, and that yeasts and other micro-organisms are important for our understanding of the ecology of insect herbivores and their evolutionary diversification. The traditional bi-trophic plant-insect niche concept must be updated to a tri-trophic niche concept, in order to accomodate for the role of micro-organisms in host-finding (Singer and Stireman 2005). This will be illustrated with results from current studies.

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