Harvey Jeffrey A, Gols Rieta, Strand Michael R
Department of Multitrophic Interactions, Netherlands Institute of Ecology, Centre for Terrestrial Ecology, Heteren, The Netherlands.
Entomol Exp Appl. 2009 Feb 9;130(3):238-248. doi: 10.1111/j.1570-7458.2008.00816.x.
In natural systems, pre-adult stages of some insect herbivores are known to be attacked by several species of parasitoids. Under certain conditions, hosts may be simultaneously parasitised by more than one parasitoid species (= multiparasitism), even though only one parasitoid species can successfully develop in an individual host. Here, we compared development, survival, and intrinsic competitive interactions amongst three species of solitary larval endoparasitoids, Campoletis sonorensis (Cameron) (Hymenoptera: Ichneumonidae), Microplitis demolitor Wilkinson, and Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), in singly parasitised and multiparasitised hosts. The three species differed in certain traits, such as in host usage strategies and adult body size. Campoletis sonorensis and M. demolitor survived equally well to eclosion in two host species that differed profoundly in size, Pseudoplusia includens (Walker) and the larger Heliothis virescens (Fabricius) (both Lepidoptera: Noctuidae). Egg-to-adult development time in C. sonorensis and M. demolitor also differed in the two hosts. Moreover, adult body mass in C. sonorensis (and not M. demolitor) was greater when developing in H. virescens larvae. We then monitored the outcome of competitive interactions in host larvae that were parasitised by one parasitoid species and subsequently multiparasitised by another species at various time intervals (0, 6, 24, and 48 h) after the initial parasitism. These experiments revealed that M. croceipes was generally a superior competitor to the other two species, whereas M. demolitor was the poorest competitor, with C. sonorensis being intermediate in this capacity. However, competition sometimes incurred fitness costs in M. croceipes and C. sonorensis, with longer development time and/or smaller adult mass observed in surviving wasps emerging from multiparasitised hosts. Our results suggest that rapid growth and large size relative to competitors of a similar age may be beneficial in aggressive intrinsic competition.
在自然系统中，已知一些食草昆虫的未成熟阶段会受到多种寄生蜂的攻击。在某些条件下，宿主可能会同时被多种寄生蜂寄生（=多重寄生），尽管在单个宿主体内只有一种寄生蜂能够成功发育。在此，我们比较了三种单独的幼虫内寄生蜂，即索诺拉 Campoletis sonorensis（卡梅伦）（膜翅目：姬蜂科）、毁侧沟茧蜂 Microplitis demolitor 威尔金森和玫烟色侧沟茧蜂 Microplitis croceipes（克雷森）（膜翅目：茧蜂科）在单寄生和多重寄生宿主中的发育、存活情况以及内在竞争相互作用。这三个物种在某些特征上存在差异，例如宿主利用策略和成虫体型。索诺拉 Campoletis sonorensis 和毁侧沟茧蜂 Microplitis demolitor 在两种体型差异极大的宿主，即甘蓝夜蛾 Pseudoplusia includens（沃克）和体型较大的烟青虫 Heliothis virescens（法布尔）（均为鳞翅目：夜蛾科）中，羽化时的存活情况相同。索诺拉 Campoletis sonorensis 和毁侧沟茧蜂 Microplitis demolitor 在这两种宿主中的卵到成虫发育时间也有所不同。此外，索诺拉 Campoletis sonorensis（而非毁侧沟茧蜂 Microplitis demolitor）在烟青虫 Heliothis virescens 幼虫体内发育时，成虫体重更大。然后，我们监测了在初次寄生后不同时间间隔（0、6、24 和 48 小时）被一种寄生蜂寄生，随后又被另一种寄生蜂多重寄生的宿主幼虫中竞争相互作用的结果。这些实验表明，玫烟色侧沟茧蜂 Microplitis croceipes 通常比其他两个物种更具竞争力，而毁侧沟茧蜂 Microplitis demolitor 是竞争力最差的，索诺拉 Campoletis sonorensis 在这方面处于中间水平。然而，竞争有时会给玫烟色侧沟茧蜂 Microplitis croceipes 和索诺拉 Campoletis sonorensis 带来适合度成本，在从多重寄生宿主中羽化存活的黄蜂中观察到发育时间延长和/或成虫体重减小。我们的结果表明，相对于年龄相似的竞争者而言，快速生长和较大体型在激烈的内在竞争中可能是有益的。
