Lang Andreas
GSF-National Research Centre for Environment and Health, Neuherberg, Institute of Soil Ecology, PO Box 1129, 85758 Oberschleissheim, Germany.
Oecologia. 2003 Jan;134(1):144-53. doi: 10.1007/s00442-002-1091-5. Epub 2002 Oct 24.
Arable land typically harbours communities of polyphagous invertebrate natural enemies, among them numerous soil-surface dwelling predators such as ground beetles (Carabidae) and spiders (Lycosidae, Linyphiidae). Numbers of these predators were experimentally manipulated in a winter wheat field in order to study the predation impact of a generalist predator assemblage on herbivorous insects, the possible interferences among the predators concerned, and subsequent effects on wheat plant parameters. Removing ground beetles doubled numbers of Lycosidae indicative of intraguild interference between these two predator groups. Aphid densities were highest in carabid removal plots implying a substantial predation impact of ground beetles on the pest population. The predation impact of ground beetles was strongest earlier and disappeared later in the season. In mid-season, at intermediate aphid densities, the combined impact of carabid beetles and spiders appeared to be responsible for the reduction in aphid abundance. This result was probably due to a biomass effect rather than to a synergistic effect of the predator community. Thysanoptera decreased when spiders were removed (perhaps because spiders were preying on a predator of thrips), while Cicadellidae and Delphacidae showed no effect at all. The rise of aphid numbers in carabid removal plots corresponded to an increase in protein content of the wheat grains, while other plant parameters such as plant numbers and grain mass were not affected. In conclusion, this study provided field evidence for intraguild interference among generalist ground predators in arable land. Despite this interference the polyphagous predator community was able to depress numbers of aphids in winter wheat, a result cascading down to plant quality parameters.
耕地通常栖息着多食性无脊椎动物天敌群落，其中有许多生活在土壤表面的捕食者，如步甲（步甲科）和蜘蛛（狼蛛科、皿蛛科）。为了研究多食性捕食者组合对食草昆虫的捕食影响、相关捕食者之间可能的干扰以及随后对小麦植株参数的影响，在一片冬小麦田中对这些捕食者的数量进行了实验性操控。移除步甲后，狼蛛数量翻倍，这表明这两类捕食者之间存在种内干扰。在移除步甲的地块中蚜虫密度最高，这意味着步甲对害虫种群有重大的捕食影响。步甲的捕食影响在季节早期最强，后期消失。在季节中期，蚜虫密度处于中等水平时，步甲和蜘蛛的综合影响似乎导致了蚜虫数量的减少。这一结果可能是由于生物量效应而非捕食者群落的协同效应。移除蜘蛛后，蓟马数量减少（可能是因为蜘蛛捕食蓟马的捕食者），而叶蝉科和飞虱科则完全没有受到影响。移除步甲的地块中蚜虫数量的增加与小麦籽粒蛋白质含量的增加相对应，而其他植株参数，如植株数量和籽粒质量则没有受到影响。总之，这项研究为耕地上多食性地面捕食者之间的种内干扰提供了田间证据。尽管存在这种干扰，多食性捕食者群落仍能够压低冬小麦田中蚜虫的数量，这一结果进而影响到植株质量参数。
