Untitled

Abstract

Our objective was to test the hypothesis that the pheromone blend and/or diel periodicity of pheromonal communication differ in populations of the nun moth, Lymantria monacha (Lepidoptera: Lymantriidae), from eastern Asia (northern Honshu, Japan) and Central Europe (Bohemia, Czech Republic). Coupled gas chromatographic-electroantennographic 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 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-methyloctadecane (disparlure). Field experiments in Honshu suggested that (+)-monachalure is the major pheromone component of L. monacha. 2me-Z7-18Hy significantly enhanced attractiveness of (+)-monachalure. Addition of (+)-disparlure to (+)-monachalure plus 2me-Z7-18Hy in Honshu and Bohemia increased attractiveness of lures by 1.2 and 20 times, respectively, indicating that (+)-disparlure is of least and most significance in the respective L. monacha populations. Moreover, capture of male L. monacha in pheromone-baited traps between 18:00 and 24:00 hr in Bohemia and 2:00 and 5:00 hr in Honshu revealed a markedly different diel periodicity of pheromonal communication. Pheromonal 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, which uses the early night for pheromonal communication and (+)-disparlure as major pheromone component. Whether communication channel divergence of L. monacha in Honshu indeed constitutes a case of reproductive character displacement is difficult to prove. The evolution of such divergence in sympatric populations of L. fumida and L. monacha would have to be demonstrated.

Lepidopteran Sex Pheromones

“…Disparlure (Me2,epo7-18:H) is a well-known pheromone identified from Lymantria dispar [3] and two other species in the same genus, L. fumida [95] and L. monacha [96]. L. monacha also secrets an unbranched derivative (epo7-18:H) [97], and a C 20 analog (Me2,epo7-20:H) has recently been found in females of another related species, L. xylina [98]. In addition to the epoxides, six methyl-branched hydrocarbons with a C 15 -C 18 main chain have been identified from four micro-lepidopteran species in Lyonetiidae (Yponomeutoidea) [99][100][101][102][103].…”

“…These Lyonetiidae pheromones possess one methyl group at the common 5-position, because the 14-position of 1,Me14-18:H and 1,Me10,Me14-18:H is represented as the 5-positon counting from the opposite terminal methyl group. Furthermore, other hydrocarbons have been discovered form macro-lepidopteran species in the rather evolved families, such as Geometridae [104][105][106][107][108], Noctuidae [109], Lymantriidae [95,97,110], and Arctiidae [111]. Me2,Z7-18:H, a pheromone component of Lymantria spp., is also a biosynthetic precursor of disparlure [112].…”

Within-population variability in a moth sex pheromone blend: genetic basis and behavioural consequences

“…Geographical variation has been found both in female signals [34][35][36][37] and male responses [22,23,38]. This suggests that moth sex pheromone signals and behavioural responses are affected by local environmental factors, although this variation may also be due to environmentally independent sexual selection.…”

Experimental evidence for interspecific directional selection on moth pheromone communication

“…Directional selection through communication interference between sympatric species that use similar premating signals has been proposed to counteract stabilizing selection (14,(19)(20)(21)(22)(23)(24)(25) and cause reproductive character displacement. In the past decade, researchers have described patterns in reproductive traits that are in accordance with reproductive character displacement, i.e., greater divergence has been found in mate recognition signals of closely related species in areas of sympatry than in areas of allopatry: in the songs of tree frogs (21,26,27), in the mate recognition cues in Drosophila (28-31) and in pheromone communication in moths (22)(23)(24).…”

“…In the past decade, researchers have described patterns in reproductive traits that are in accordance with reproductive character displacement, i.e., greater divergence has been found in mate recognition signals of closely related species in areas of sympatry than in areas of allopatry: in the songs of tree frogs (21,26,27), in the mate recognition cues in Drosophila (28-31) and in pheromone communication in moths (22)(23)(24). However, these studies fall short of addressing whether selection due to interspecific interference could have been strong enough to overcome stabilizing selection by conspecifics.…”