Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2001
Publication Date: 11/20/2001
Citation: Gries, G., Schaefer, P.W., Gries, R., Liska, J., Gotoh, T. 2001. Character displacement in lymantria monach from northern japan? Journal of Chemical Ecology. 27(6):1163-1176. Interpretive Summary: The nun moth, Lymantria monacha, of Europe and Asia is one forest pest that has not yet invaded North America. The caterpillar defoliates many conifers, so its introduction into western states would probably be disastrous. During recent field studies into the sex pheromone communication of nun moths in both Europe and Japan, we determined that subtle differences exist in populations of nun moths from opposite ends of the normal distribution range. Although males respond to the same essential female sex pheromone blend, field evidence suggests that the significance of the various components is not uniform. Based on chemical communication, we can recognize two behavioral forms. Furthermore, these two moth forms show distinctly different nocturnal periodicity as well -- European form responding to sex pheromone lures in the early evening hours while the Japanese form responds in the early morning hours. We propose that these differences have resulted as a direct consequence of behavioral competition with Lymantria fumida, a sympatric, coseasonal, competitor found in Japan but absent in Europe. We suggest that this is an example of character displacement among congeneric moths.
Technical Abstract: This study tested the hypothesis that the pheromone blend and/or diel periodicity of pheromonal communication differ in populations of the nun moth, Lymantria monacha (L) (Lepidoptera: Lymantriidae), from East Asia (Honshu, Japan) and Central Europe (Bohemia, Czech Republic). Coupled gas chromatograph-electroantennogram detection (GC-EAD) analyses of pheromone gland extract of female L. monacha from Japan confirmed the presence of compounds previously identified in pheromone extracts of L. monacha from the Czech Republic, as follows: (Z) -7-octadececene, 2-methyl -(Z)-7- octadecene (2me-Z7-18Hy), cis-7,8-epoxy-octadecane (monachalure), and cis-7,8-epoxy-2methlyloctadecane (disparlure). In field experiments in Japan, (+)-monachaulure proved to be the major pheromone component of L. monacha. 2Me-Z7-18Hy significantly enhanced attractiveness of (+) - monachalure. Addition of (+)-disparlure to (+)-monachalure plus 2me-Z7-18 Hy in Japan and the Czech Republic increased attractiveness of lures by 1. and 20 times, respectively, showing that (+)-disparlure is of little and great importance in the respective L. monacha populations. Moreover, capture of male L. monacha in pheromone baited traps between 18:00 and 24:00 hr in the Czech Republic and between 1:00 and 5:00 hr in Japan revealed markedly different diel periodicities in pheromonal communication Pheromonal communication late at night and use of (+) -monachalure, rather than (+)-disparlure, as major pheromone component by L monacha in Japan may have resulted from interspecific competition with coseasonal L. fumida, which uses the early night for pheromonal communcation and (+)-disparlure as major pheromone component.