Juen Anita, Traugott Michael
Centre is for Mountain Agriculture, University of Innsbruck, Technikerstrasse 13, 6020 Innsbruck, Austria.
Oecologia. 2005 Jan;142(3):344-52. doi: 10.1007/s00442-004-1736-7. Epub 2004 Oct 29.
White grubs (larvae of Coleoptera: Scarabaeidae) are abundant in below-ground systems and can cause considerable damage to a wide variety of crops by feeding on roots. White grub populations may be controlled by natural enemies, but the predator guild of the European species is barely known. Trophic interactions within soil food webs are difficult to study with conventional methods. Therefore, a polymerase chain reaction (PCR)-based approach was developed to investigate, for the first time, a soil insect predator-prey system. Can, however, highly sensitive detection methods identify carrion prey in predators, as has been shown for fresh prey? Fresh Melolontha melolontha (L.) larvae and 1- to 9-day-old carcasses were presented to Poecilus versicolor Sturm larvae. Mitochondrial cytochrome oxidase subunit I fragments of the prey, 175, 327 and 387 bp long, were detectable in 50% of the predators 32 h after feeding. Detectability decreased to 18% when a 585 bp sequence was amplified. Meal size and digestion capacity of individual predators had no influence on prey detection. Although prey consumption was negatively correlated with cadaver age, carrion prey could be detected by PCR as efficiently as fresh prey irrespective of carrion age. This is the first proof that PCR-based techniques are highly efficient and sensitive, both in fresh and carrion prey detection. Thus, if active predation has to be distinguished from scavenging, then additional approaches are needed to interpret the picture of prey choice derived by highly sensitive detection methods.
蛴螬（鞘翅目：金龟科幼虫）在地下系统中数量众多，会通过啃食根部对多种作物造成相当大的损害。蛴螬种群可能受到天敌的控制，但欧洲蛴螬物种的捕食者群落却鲜为人知。利用传统方法很难研究土壤食物网中的营养相互作用。因此，首次开发了一种基于聚合酶链反应（PCR）的方法来研究土壤昆虫捕食者 - 猎物系统。然而，高灵敏度的检测方法能否像对新鲜猎物那样识别捕食者体内的腐肉猎物呢？将新鲜的五月鳃金龟幼虫和1至9日龄的尸体提供给杂色步甲幼虫。喂食32小时后，在50%的捕食者体内可检测到长度为175、327和387 bp的猎物线粒体细胞色素氧化酶亚基I片段。当扩增585 bp序列时，可检测性降至18%。单个捕食者的食量和消化能力对猎物检测没有影响。尽管猎物消耗量与尸体年龄呈负相关，但无论腐肉年龄如何，通过PCR都能像检测新鲜猎物一样高效地检测到腐肉猎物。这首次证明了基于PCR的技术在检测新鲜和腐肉猎物方面都非常高效且灵敏。因此，如果必须区分主动捕食和食腐行为，那么需要额外的方法来解读通过高灵敏度检测方法得出的猎物选择情况。
