Inheritance of Olfactory Preferences I. Pheromone-Mediated Behavioral Responses of Heliothis subflexa × Heliothis virescens Hybrid Male Moths

Abstract

Shifts in male preference for qualitatively different pheromone blends appear to have played a fundamental role in the divergence of olfactory communication and evolution of moth species. As an initial step in documenting the genetic complexity underlying such shifts, we characterized the behavioral responses of hybrid male moths created by mating two heliothine moth species, Heliothis subflexa and Heliothis virescens. Between 67 and 96% of hybrid males flew upwind and contacted the pheromone source when presented with a blend consisting of (Z)-11-hexadecenal (Z11–16:Ald), (Z)-9-hexadecenal (Z9–16:Ald), and (Z)-11-hexadecenol (Z11–16:OH) in a 1:0.5:0.1 ratio that has previously been shown to be attractive to H. subflexa males. In addition, an H. virescens blend of Z11–16:Ald and (Z)-9-tetradecenal (Z9–14:Ald) enhanced by the addition of Z11–16:OH (in a 1:0.05:0.1 mixture) was attractive to hybrid males (26–64% source contact), but significantly fewer males reached the odor source compared to the blend containing Z9–16:Ald. A blend in which the dosage of Z9–14:Ald was doubled, however, was equally attractive (75–77% source contact) as the Z9–16:Ald-containing blend. Consecutive presentation of two blends revealed that individual hybrid males responded equally well to blends containing either Z9–14:Ald or Z9–16:Ald. Together these results suggest that in addition to Z11–16:Ald, hybrid males: (1) required either Z9–16:Ald (likeH. subflexamales) or Z9–14:Ald (like H. virescens males); (2) required the presence of Z11–16:OH (H. subflexa dominant); (3) were not adversely affected by the presence of Z11–16:Ac (H. subflexa dominant). The behavioral response phenotype of hybrid males was therefore influenced by genetic factors inherited from both parental species.