Reproductive character displacement in Lymantria monacha from northern Japan?

Our objective was to test the hypothesis that the pheromone blend and/or di el periodicity of pheromonal communication differ in populations of the nun moth, Lymantria monacha (Lepidoptera: Lymantriidae), from eastern Asia (no rthern Honshu, Japan) and Central Europe (Bohemia, Czech Republic). Coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses of p heromone gland extract of female L monacha from Japan confirmed the presenc e of compounds previously identified in pheromone extracts of L. monacha fr om Bohemia, as follows: (Z)-7-octadecene, 2-methyl-(Z)-7-octadecene (2me-Z7 -18Hy), cis-7,8-epoxy-octadecane (monachalure), and cis-7,8-epoxy-2-methylo ctadecane (disparlure). Field experiments in Honshu suggested that (+)-mona chalure is the major pheromone component of L. monacha. 2me-Z7-18Hy signifi cantly enhanced attractiveness of (+)-monachalure. Addition of (+)-disparlu re to (+)-monachalure plus 2me-Z7-18Hy in Honshu and Bohemia increased attr activeness of lures by 1.2 and 20 times, respectively, indicating that (+)- disparlure is of least and most significance in the respective L monacha po pulations. Moreover, capture of male L. monacha in pheromone-baited traps b etween 18:00 and 24:00 hr in Bohemia and 2:00 and 5:00 hr in Honshu reveale d a markedly different diel periodicity of pheromonal communication. Pherom onal communication late at night and use of (+)-monachalure, rather than ()-disparlure, as the major pheromone component by L. monacha in Honshu may have resulted from interspecific competition with coseasonal L. fumida, whi ch uses the early night for pheromonal communication and (+)-disparlure as major pheromone component. Whether communication channel divergence of L. m onacha in Honshu indeed constitutes a case of reproductive character displa cement is difficult to prove. The evolution of such divergence in sympatric populations of L. fumida and L. monacha would have to be demonstrated.