Geographic variation in the field response of male European pine sawflies,Neodiprion sertifer, to different pheromone stereoisomers and esters

The European pine sawfly, Neodiprion sertifer (Geoffroy) (Hymenoptera: Dipr ionidae), is a widespread and economically important forest insect. The sex pheromone communication system of this species has been previously investi gated in North America, Japan and Europe, with the acetate or propionate of the alcohol (2S,3S,7S)-3,7-dimethyl-2-pentadecanol (diprionol) shown to be the main pheromone component. In some locations, male attraction either in creased or decreased by the addition of the (2S,3R,7R)-diprionyl acetate is omer. However, these studies were made with different batches of synthetic pheromones, with different types of traps and according to different proced ures, so the observed differences might not reflect true geographic variati on. Here we investigate the geographic pattern of male sawfly response by u sing identical chemicals, traps and experimental procedures at eight field sites ranging from Japan in the east to Canada in the west. We found an inc reased inhibitory effect of the (2S,3R,7R)-isomer from Japan and Siberia to Europe. At the eastern sites, increasing amounts of the (2S,3R,7R)-isomer up to and equal to the amount of the (2S,3S,7S )-isomer, did not influence the trap catch, whereas at sites in Europe, as little as 1% of the (2S,3R,7 R)-isomer almost completely inhibited the attraction. The response of the N orth American population was intermediate. The only site in which the (2S,3 R,7R)-isomer was essential for the attraction of males was in Siberia. A si milar pattern was found for the (2S,3R,7S)-isomer. Both the acetate and the propionate form of the (2S,3S,7S)-isomer were attractive by themselves in Japan, Europe and North America, and neither the (2S,3R,7S)-isomer nor the (2S,3R,7R)-isomer alone were attractive, in the acetate or propionate form. We discuss the significance of our findings for the development of more ef ficient monitoring schemes and for the causes of population divergence and speciation in the European pine sawfly.