Early quality assessment lessens pheromone specificity in a moth

Abstract

Pheromone orientation in moths is an exemplar of olfactory acuity. To avoid heterospecific mating, males respond to femaleproduced blends with high specificity and temporal resolution. A finely tuned sensory to projection neuron network secures specificity, and this network is thought to assess pheromone quality continually during orientation. We tested whether male moths do indeed evaluate each pheromone encounter and surprisingly found that male European corn borer moths instead generalize across successive encounters. Although initially highly ratio specific, once "locked on" to the pheromone plume the acceptable ratio can vary widely, and even unattractive blends can become attractive. We further found that this "mental shortcut" may be a consequence of the fact that sensory neurons exposed to frequent encounters do not reliably encode blend ratios. Neurons tuned to either of the two pheromone components adapt differentially in plumes containing the preferred blend ratio (97:3) and cause the olfactory sensory signal to "evolve," even in narrowly tuned pheromonal circuits. However, apparently the brain interprets these shifting signals as invariant "gestalts." Generalization in pheromone perception may mitigate stabilizing selection and allow introgression between sympatric strains, such as in the European corn borer, that otherwise appear isolated by pheromonal differences. Generalization may also be important in responses to general odorants, as circuits underlying these display vast sensitivity differences, complex interactions, and temporal intricacies.blend recognition | odor processing | sensory constraints | evolution | sexual selection

Co‐localization of insect olfactory sensory cells improves the discrimination of closely separated odour sources

“…; Kárpáti et al . ). The difference in distance range might reflect a difference in resolution between the olfactory senses of moths and beetles (Andersson et al .…”

Genetic mapping of male pheromone response in the European corn borer identifies candidate genes regulating neurogenesis

“…This approach has been justified by the observation that E-strain males may exhibit earlier signs of attention to the Z lure and the opposite applies to Z-strain males; such signs are unreliable predictors of the final outcome (38). However, recent studies have shown that early responses by Z-strain males can lock them in to subsequent behaviors that are maintained even if the pheromone lure is experimentally switched from Z to E while the moth is in midflight (40). Thus, variation in the early responses also may be a relevant indicator of genetic differences between the Z and E strains.…”

Intraspecific Combinations of Flower and Leaf Volatiles Act Together in Attracting Hawkmoth Pollinators

“…In moths, behavioral responses of males to sex pheromones have been well investigated [1]. The pheromone cocktail emitted by females usually contains several compounds, the ratio of which is crucial for male attraction [2], [3]. Male attraction to sex pheromones can, however, be augmented by presenting the pheromone against a relevant leaf volatile blend emitted by a suitable larval host plant [4], [5].…”