Fox Laurel R, Letourneau Deborah K, Eisenbach Jamin, Van Nouhuys Saskya
Department of Biology, University of California, 95064, Santa Cruz, CA, USA.
Environmental Studies Board, University of California, 95064, Santa Cruz, CA, USA.
Oecologia. 1990 Jun;83(3):414-419. doi: 10.1007/BF00317569.
We studied interactions among collards, Brassica oleracea var. acephala, the diamondback moth (DBM), Plutella xylostella (Lepidoptera: Yponomeutidae) and its parasitoid Diadegma insulare (Hymenoptera: Ichneumonidae) by manipulating plant nitrogen (N) concentrations in field and laboratory experiments. Parasitoid abundance strongly reflected DBM abundance and was related to total leaf N. Parasitism rates were high (70.7%) and density-independent. Wasp sex ratios varied markedly (3-93% female) in response to the herbivores, the plants, or both. Higher proportions of female wasps emerged from DBM larvae on plants with high leaf N than on unfertilized plants. More female wasps also emerged from larvae parasitized as larger instars. We suggest that wasps have the potential to control DBM populations through long-term numerical responses mediated by variable sex ratios.
我们通过在田间和实验室实验中操控植物的氮（N）浓度，研究了羽衣甘蓝（Brassica oleracea var. acephala）、小菜蛾（DBM，Plutella xylostella，鳞翅目：菜蛾科）及其寄生蜂岛甲腹茧蜂（Diadegma insulare，膜翅目：姬蜂科）之间的相互作用。寄生蜂的数量强烈反映了小菜蛾的数量，并且与叶片总氮含量有关。寄生率很高（70.7%）且与密度无关。黄蜂的性别比例因食草动物、植物或两者的影响而有显著差异（雌性占3 - 93%）。与未施肥的植物相比，在叶片含氮量高的植物上，从小菜蛾幼虫中羽化出的雌性黄蜂比例更高。从较大龄期被寄生的幼虫中羽化出的雌性黄蜂也更多。我们认为，黄蜂有可能通过由可变性别比例介导的长期数量反应来控制小菜蛾种群。
