IPS pini: The basis for interpopulational differences in pheromone biology

Abstract

Ips pini from Idaho (ID) produce (−)-ipsdienol and respond to it in the laboratory.I. pini from New York (NY) produce (+) and (−)-ipsdienol in a 65∶35 ratio and respond much more strongly to the (+) than to the (−) enantiomer. Response byI. pini-ID to (−)-ipsdienol in the laboratory was inhibited by (+)-ipsdienol, while the field response byI. pini-NY was optimal to a 50:50 mixture of (+) and (−)-ipsdienol. This differential production and response to enantiomers of ipsdienol is sufficient to account for populational specificity observed in earlier experiments and confirmed by our current work. Reciprocal hybrids of the NY and IDI. pini populations did not differ in their patterns of attraction and response; those of both types of F1 were similar to NY beetles. Thus, it appears that (+)-ipsdienol is produced by the hybrids and is necessary for their maximum response, but this supposition was not tested. The genes controlling the pheromone biology ofI. pini are not sex linked. Since previous whole-antenna and single-cell electrophysiological data show that the receptor systems of the two populations are virtually identical, response behavior seems to be governed by the central nervous system rather than by the characteristics of the olfactory receptors.