Centre for Evolutionary Biology, School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia.
Harry Butler Institute, Murdoch University, Perth, WA 6150, Australia.
J Exp Biol. 2022 Aug 1;225(15). doi: 10.1242/jeb.244375. Epub 2022 Aug 5.
The often complex cocktails of hydrocarbon compounds found on the cuticles of insects can serve both naturally and sexually selected functions, contributing to an individual's ability to withstand water loss and attract mating partners. However, whether natural and sexual selection act synergistically or antagonistically on a species' cuticular hydrocarbon (CHC) profile remains unclear. Here, we examined the ontogeny of the CHC profile in a species of cricket, Teleogryllus oceanicus, while manipulating humidity during development. We predicted that juvenile crickets should produce only those compounds that contribute to desiccation resistance, while those compounds contributing specifically to male attractiveness should be produced only at sexual maturity. Further, if attractive CHCs come at a cost to desiccation resistance as predicted by some models of sexual selection, then males reared under low humidity should be constrained to invest less in attractive CHCs. Crickets reared under low humidity produced more long-chain methyl-branched alkanes, alkenes and alkadienes than did crickets reared under high humidity. The abundance of n-alkanes was unaffected by humidity treatment. Sexual dimorphism in the CHC profile was not apparent until adult emergence and became exaggerated 10 days after emergence, when crickets were sexually mature. Males produced more of the same compounds that were increased in both sexes under low humidity, but the humidity treatment did not interact with sex in determining CHC abundance. The data suggest that CHC profiles which protect crickets from desiccation might have synergistic effects on male attractiveness, as there was no evidence to suggest males trade-off a CHC profile produced in response to low humidity for one associated with sexual signalling.
昆虫表皮上发现的烃类化合物混合物通常很复杂，具有自然和性选择功能，有助于个体抵抗失水和吸引交配伴侣的能力。然而，自然选择和性选择是否协同或拮抗地作用于一个物种的表皮烃（CHC）特征仍然不清楚。在这里，我们研究了蟋蟀 Teleogryllus oceanicus 物种的 CHC 特征的个体发生，同时在发育过程中操纵湿度。我们预测，幼年蟋蟀应该只产生那些有助于抗干燥的化合物，而那些专门有助于雄性吸引力的化合物应该只在性成熟时产生。此外，如果像一些性选择模型所预测的那样，有吸引力的 CHC 以抗干燥能力为代价，那么在低湿度下饲养的雄性应该会限制在有吸引力的 CHC 上的投资。在低湿度下饲养的蟋蟀比在高湿度下饲养的蟋蟀产生了更多的长链甲基支链烷烃、烯烃和二烯烃。n-烷烃的丰度不受湿度处理的影响。CHC 特征的性二态性直到成虫出现才变得明显，并在成虫出现 10 天后变得更加夸张，此时蟋蟀已经性成熟。与在高湿度下饲养的蟋蟀相比，雄性产生了更多的相同化合物，但湿度处理并没有与性别相互作用来确定 CHC 的丰度。这些数据表明，保护蟋蟀免受干燥的 CHC 特征可能对雄性吸引力有协同作用，因为没有证据表明雄性会为了应对低湿度而牺牲与性信号相关的 CHC 特征。
