Birkhofer K, Gavish-Regev E, Endlweber K, Lubin Y D, von Berg K, Wise D H, Scheu S
Zoological Institute, Darmstadt University of Technology, Darmstadt, Germany.
Bull Entomol Res. 2008 Jun;98(3):249-55. doi: 10.1017/S0007485308006019. Epub 2008 Apr 28.
Generalist predators contribute to pest suppression in agroecosystems. Spider communities, which form a substantial fraction of the generalist predator fauna in arable land, are characterized by two functional groups: web-building and cursorial (non-web-building) species. We investigated the relative impact of these two functional groups on a common pest (Sitobion avenae, Aphididae) in wheat by combining a molecular technique that revealed species-specific aphid consumption rates with a factorial field experiment that analyzed the impact, separately and together, of equal densities of these two spider functional groups on aphid population growth. Only cursorial spiders retarded aphid population growth in our cage experiment, but this effect was limited to the initial aphid-population growth period and low-to-intermediate aphid densities. The molecular analysis, which used aphid-specific primers to detect aphid DNA in predator species, detected the highest proportion of aphid-consuming individuals in two cursorial spiders: the foliage-dwelling Xysticus cristatus (Thomisidae) and the ground-active Pardosa palustris (Lycosidae). The results suggest that manipulating the community composition in favour of pest-consuming functional groups may be more important for improving biological control than fostering predator biodiversity per se. Agricultural management practices that specifically foster effective species or functional groups (e.g. mulching for cursorial spiders) should receive more attention in low-pesticide farming systems.
多面手捕食者有助于抑制农业生态系统中的害虫。蜘蛛群落是耕地中多面手捕食性动物区系的重要组成部分，其特征为两个功能组：结网型和游猎型（非结网型）物种。我们通过将一种揭示特定物种蚜虫消耗率的分子技术与一项析因田间试验相结合，来研究这两个功能组对小麦中一种常见害虫（麦长管蚜，蚜科）的相对影响。该田间试验分别及共同分析了这两个蜘蛛功能组的同等密度对蚜虫种群增长的影响。在我们的网室试验中，只有游猎型蜘蛛抑制了蚜虫种群增长，但这种影响仅限于蚜虫种群增长初期以及低至中等蚜虫密度时。分子分析使用蚜虫特异性引物来检测捕食者物种中的蚜虫DNA，在两种游猎型蜘蛛中检测到消耗蚜虫个体的比例最高：栖息于叶片上的茶色新圆蛛（蟹蛛科）和活跃于地面的沼地豹蛛（狼蛛科）。结果表明，与促进捕食者生物多样性本身相比，操纵群落组成以利于消耗害虫的功能组对于改善生物防治可能更为重要。在低农药种植系统中，应更多关注那些专门培育有效物种或功能组的农业管理措施（例如为游猎型蜘蛛覆盖地膜）。
