Jonsson M, Wratten S D, Robinson K A, Sam S A
Bio-Protection Research Centre, PO Box 84, Lincoln University, Lincoln 7647, New Zealand.
Bull Entomol Res. 2009 Jun;99(3):275-85. doi: 10.1017/S0007485308006275. Epub 2008 Dec 9.
Omnivory is common among arthropods, but little is known about how availability of plant resources and prey affects interactions between species operating at the third and fourth trophic level. We used laboratory and field cage experiments to investigate how the provision of flowers affects an omnivorous lacewing, Micromus tasmaniae (Hemerobiidae) and its parasitoid Anacharis zealandica (Figitidae). The adult lacewing is a true omnivore that feeds on both floral resources and aphids, whereas the parasitoid is a life-history omnivore, feeding on lacewing larvae in the larval stage and floral nectar as an adult. We showed that the effect of floral resources (buckwheat) on lacewing oviposition depends on prey (aphid) density, having a positive effect only at low prey density and that buckwheat substantially increases the longevity of the adult parasitoid. In field cages, we tested how provision of flowering buckwheat affects the dynamics of a four trophic level system, comprising parasitoids, lacewings, pea aphids and alfalfa. We found that provision of buckwheat decreased the density of lacewings in the first phase of the experiment when the density of aphids was high. This effect was probably caused by increased rate of parasitism by the parasitoid, which benefits from the presence of buckwheat. Towards the end of the experiment when the aphid populations had declined to low levels, the effect of buckwheat on lacewing density became positive, probably because lacewings were starving in the no-buckwheat treatment. Although presence of buckwheat flowers did not affect aphid populations in the field cages, these findings highlight the need to consider multitrophic interactions when proposing provision of floral resources as a technique for sustainable pest management.
杂食性在节肢动物中很常见，但对于植物资源和猎物的可利用性如何影响处于第三和第四营养级的物种之间的相互作用，我们却知之甚少。我们通过实验室和田间网笼实验，来研究提供花朵如何影响杂食性草蛉（Micromus tasmaniae，草蛉科）及其寄生蜂（Anacharis zealandica，广肩小蜂科）。成年草蛉是真正的杂食性动物，既取食花卉资源也取食蚜虫，而寄生蜂在生活史中也是杂食性的，幼虫阶段取食草蛉幼虫，成虫则取食花蜜。我们发现，花卉资源（荞麦）对草蛉产卵的影响取决于猎物（蚜虫）密度，仅在低猎物密度时具有积极影响，且荞麦能显著延长成年寄生蜂的寿命。在田间网笼中，我们测试了提供开花荞麦如何影响一个包含寄生蜂、草蛉、豌豆蚜和苜蓿的四营养级系统的动态变化。我们发现，在实验的第一阶段，当蚜虫密度较高时，提供荞麦会降低草蛉的密度。这种影响可能是由寄生蜂寄生率的增加导致的，寄生蜂因荞麦的存在而受益。在实验接近尾声时，当蚜虫数量下降到较低水平时，荞麦对草蛉密度的影响变为积极的，这可能是因为在无荞麦处理中草蛉处于饥饿状态。尽管田间网笼中荞麦花的存在并未影响蚜虫数量，但这些发现凸显了在将提供花卉资源作为一种可持续害虫管理技术提出时，需要考虑多营养级相互作用。
