Cuticular Hydrocarbons of Six Geographic Populations of Ips subelongauts in Northeastern China: Similarities and Evolutionary Hints

The Asian larch bark beetle, <i>I. subelongatus</i> Motschulsky, is a severe pest of various <i>Larix</i> species in its natural range. This study reports the degree of similarity among cuticular hydrocarbon (CHC) profiles of six populations of <i>I. subelongatus</i> in northeastern China. Thirty individual or isomeric mixtures of hydrocarbons were identified by solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The hydrocarbon components consist of straight-chain alkanes, alkenes, and methyl-branched hydrocarbons with carbon chain lengths ranging from 24 to 31. Among these, four CHCs (<i>n</i>-C₂₅, 9-C_27:1, <i>n</i>-C₂₇, and 3-meC₂₇) can serve as chemotaxonomic markers to identify <i>I. subelongatus</i>. No qualitative differences were detected between males and females in any of the six populations, but significant quantitative differences were observed in some CHCs. Phylogenetic analysis based on CHC profiles showed only minor differences compared to analysis based on partial mtDNA COI sequences regarding bark beetle species affinity. These results establish a rapid chemotaxonomic method and provide a basis for further investigations into the functions of CHCs in <i>I. subelongatus</i>.