Effects of genotype and host environment on the cuticular hydrocarbon profiles of Lysiphlebus parasitoids and aggression by aphid-tending ants

Parasitoids in the genus Lysiphlebus specialize on ant-tended aphids and have previously been reported to mimic the CHC profiles of their aphid hosts to avoid detection by ants. However, the precise mechanisms that mediate reduced ant aggression toward Lysiphlebus spp. are not known, nor is it clear whether such mechanisms are broadly effective or specialized to particular aphid hosts. Here we explore the effects of wasp genotype and host environment on Lysiphlebus cuticular hydrocarbon (CHC) profiles and ant aggression. Rearing asexual Lysiphlebus lines in different host aphid environments revealed effects of both wasp line and aphid host on wasp CHCs. However, variation in genotype and host affected different features of the CHC profile, with wasp genotype explaining most variation in linear and long-chain methyl alkanes, while aphid host environment primarily influenced short-chain methyl alkanes. Subsequent behavioral experiments revealed no effects of host environment on ant aggression, but stronger evidence for genotypic effects. The presence of genotypic variation in experienced ant aggression and relevant chemical traits is particularly relevant in light of recent evidence for genetic divergence among Lysiphlebus parasitoids collected from different aphid hosts.

Lysiphlebus属寄生蜂专性寄生蚁护蚜虫，既往研究表明该类寄生蜂可模拟其寄主蚜虫的表皮碳氢化合物（cuticular hydrocarbon, CHC）谱，以躲避蚂蚁的侦测。然而，介导蚂蚁对Lysiphlebus属寄生蜂攻击行为减弱的精确机制仍未阐明，且此类机制究竟是具有广谱适用性，还是仅针对特定蚜虫寄主，目前仍不明确。本研究探讨了寄生蜂基因型与寄主环境对Lysiphlebus属昆虫CHC谱及蚂蚁攻击行为的影响。通过在不同蚜虫寄主环境下培养无性系Lysiphlebus品系，研究发现寄生蜂品系与蚜虫寄主均会对寄生蜂的CHC谱产生影响。不过，基因型与寄主环境分别作用于CHC谱的不同特征：寄生蜂基因型可解释线性长链甲基烷烃的绝大多数变异，而蚜虫寄主环境则主要影响短链甲基烷烃的变异。后续行为实验结果显示，寄主环境对蚂蚁的攻击行为无显著影响，但有更充分的证据表明基因型可产生显著作用。鉴于近期有研究发现，从不同蚜虫寄主中采集的Lysiphlebus属寄生蜂存在遗传分化，因此寄生蜂在蚂蚁攻击行为与相关化学性状上的基因型变异，其研究意义尤为突出。