Ngumbi E, Fadamiro H
Department of Entomology and Plant Pathology, Auburn University, AL 36849, USA.
Bull Entomol Res. 2012 Dec;102(6):710-8. doi: 10.1017/S0007485312000326. Epub 2012 May 30.
The relationship between the degree of specialization of parasitoids and their responses to host-related volatiles is an important and current evolutionary question. Specialist parasitoids which have evolved to attack fewer host species are predicted to be more responsive to host-related volatiles than generalists. We tested the above prediction by comparing behavioural responses of both sexes of two parasitoids (Hymenoptera: Braconidae) with different degrees of host specificity, Microplitis croceipes (Cresson) (specialist) and Cotesia marginiventris (generalist), to different suites of synthetic host-related volatile compounds. The compounds tested at two doses (1 and 100 μg) include two green leaf volatiles (GLVs: hexanal and (Z)-3-hexen-1-ol) and four herbivore-induced plant volatiles (HIPVs: (Z)-3-hexenyl acetate, linalool, (Z)-3-hexenyl butyrate and (E,E)-α-farnesene). Two hypotheses were tested: (i) M. croceipes (specialist) would show relatively greater behavioural responses to the HIPVs, whereas C. marginiventris (generalist) would show greater behavioural responses to the GLVs, and (ii) females of both species would show greater responses than conspecific males to the host-related volatiles. At the low dose (1 μg), females of the specialist showed significantly greater responses than females of the generalist to three of the tested HIPVs, (Z)-3-hexenyl acetate, linalool and (Z)-3-hexenyl butyrate. In contrast, females of the generalist showed relatively greater responses to the GLVs. The same trends were recorded at the high dose but fewer significant differences were detected. In general, similar results were recorded for males, with the exception of linalool (an HIPV) which elicited significantly greater response in the generalist than the specialist. Comparing the sexes, females of both species showed greater responses than conspecific males to most of the tested volatiles. The ecological significance of these findings is discussed.
寄生蜂的专业化程度与其对寄主相关挥发物的反应之间的关系是一个重要且当前备受关注的进化问题。相较于广食性寄生蜂，进化为攻击较少寄主物种的专食性寄生蜂预计对寄主相关挥发物的反应更强烈。我们通过比较两种具有不同寄主专一性程度的寄生蜂（膜翅目：茧蜂科）——玫烟色瘤姬蜂（Microplitis croceipes，Cresson，专食性）和侧沟茧蜂（Cotesia marginiventris，广食性）——两性对不同组合的合成寄主相关挥发性化合物的行为反应，来检验上述预测。在两种剂量（1微克和100微克）下测试的化合物包括两种绿叶挥发物（GLVs：己醛和(Z)-3-己烯-1-醇）以及四种植食性昆虫诱导的植物挥发物（HIPVs：(Z)-3-己烯基乙酸酯、芳樟醇、(Z)-3-己烯基丁酸酯和(E,E)-α-法尼烯）。检验了两个假设：（i）玫烟色瘤姬蜂（专食性）对HIPVs的行为反应相对更强，而侧沟茧蜂（广食性）对GLVs的行为反应更强，以及（ii）两个物种的雌性对寄主相关挥发物的反应都比对同种雄性的反应更强。在低剂量（1微克）时，专食性的雌性对三种测试的HIPVs，即(Z)-3-己烯基乙酸酯、芳樟醇和(Z)-3-己烯基丁酸酯的反应显著强于广食性的雌性。相比之下，广食性的雌性对GLVs的反应相对更强。在高剂量时也记录到了相同的趋势，但检测到的显著差异较少。总体而言，雄性也记录到了类似的结果，但芳樟醇（一种HIPV）除外，它在广食性中的反应显著强于专食性。比较两性，两个物种的雌性对大多数测试挥发物的反应都比对同种雄性的反应更强。讨论了这些发现的生态意义。
