Differentiation of the volatiles from a host plant fed upon by the adults of two Anoplophora species and their impacts on beetle behavior

Anoplophora glabripennis and Anoplophora chinensis are important wood-boring pests in China, damaging the same host species in many areas. Previous studies have shown that the adults of two species can mate when they encounter, whereas interspecific mating is rare when they coexist freely on host branches, suggesting the presence of unknown mechanism that can reduce the encountering probability of two species on the same host. It has been found that the volatiles released from the wounds caused by adult feeding are attractive to the adults in both species. In this study, the behavioral responses of the adults of two Anoplophora species to the volatiles released from Acer negundo twigs fed upon by two species were investigated using indoor olfactory bioassays, and the chemical compositions of the volatiles from the A. negundo twigs fed upon by male and female A. glabripennis and A. chinensis were analyzed using Gas chromatography-mass spectrometry (GC-MS). The purpose of this study is to determine whether there is differentiation in the chemical compositions of the volatiles released from the same host twigs fed upon by two species, and whether the attractions of these volatiles have species-specificity, which may help reduce the encounters between each other on the same host. The results from the olfactory bioassays showed that both species were more attracted to the volatiles released from the beetle-fed twigs than those from unfed twigs. When the volatiles from the twigs fed upon by two species coexisted, the females of both species were significantly more attracted to the volatiles from the conspecific-fed twigs than those from the interspecific-fed twigs, but this preference was not clearly observed in the males of two species. Chemical analyses indicated that the relative contents of some compounds significantly differed in the volatiles released from the twigs fed upon by two species. Ethylacetophenone and α-farnesene were only detected in the volatiles from the twigs fed upon by A. glabripennis, and the relative contents of decanal and n-hexadecanoic acid were significantly higher in the volatiles from the twigs fed upon by A. glabripennis. The relative contents of β-ocimene, n-nonanal and 4-ethylbenzaldehyde were significantly higher in the volatiles from the twigs fed upon by A. chinensis. The results of this study suggest that feeding by the adults of two Anoplophora species can cause the release of differential volatiles from the same host twigs, and the activities of these volatiles have interspecific specificity, which may help two species reduce interspecific mating interference and achieve sympatric coexistence.