Nitschke Norma, Allan Eric, Zwölfer Helmut, Wagner Lysett, Creutzburg Sylvia, Baur Hannes, Schmidt Stefan, Weisser Wolfgang W
Institute of Ecology Friedrich-Schiller-University Jena Germany.
Institute of Plant Sciences University of Bern Bern Switzerland.
Ecol Evol. 2017 Oct 5;7(22):9319-9332. doi: 10.1002/ece3.3142. eCollection 2017 Nov.
High biodiversity is known to increase many ecosystem functions, but studies investigating biodiversity effects have more rarely looked at multi-trophic interactions. We studied a tri-trophic system composed of (brown knapweed), its flower head-infesting tephritid fruit flies and their hymenopteran parasitoids, in a grassland biodiversity experiment. We aimed to disentangle the importance of direct effects of plant diversity (through changes in apparency and resource availability) from indirect effects (mediated by host plant quality and performance). To do this, we compared insect communities in transplants, whose growth was influenced by the surrounding plant communities (and where direct and indirect effects can occur), with potted plants, which do not compete with the surrounding plant community (and where only direct effects are possible). Tephritid infestation rate and insect load, mainly of the dominant species , decreased with increasing plant species and functional group richness. These effects were not seen in the potted plants and are therefore likely to be mediated by changes in host plant performance and quality. Parasitism rates, mainly of the abundant chalcid wasps and , increased with plant species or functional group richness in both transplants and potted plants, suggesting that direct effects of plant diversity are most important. The differential effects in transplants and potted plants emphasize the importance of plant-mediated direct and indirect effects for trophic interactions at the community level. The findings also show how plant-plant interactions critically affect results obtained using transplants. More generally, our results indicate that plant biodiversity affects the abundance of higher trophic levels through a variety of different mechanisms.
众所周知，高生物多样性会增强许多生态系统功能，但研究生物多样性影响的研究很少关注多营养级相互作用。在一项草地生物多样性实验中，我们研究了一个由（褐矢车菊）、其花头寄生的实蝇及其膜翅目寄生蜂组成的三营养级系统。我们旨在区分植物多样性的直接影响（通过外观和资源可用性的变化）与间接影响（由寄主植物质量和性能介导）的重要性。为此，我们将受周围植物群落影响生长的（直接和间接影响都可能发生）移植植物中的昆虫群落与不与周围植物群落竞争的盆栽植物中的昆虫群落进行了比较（仅可能产生直接影响）。实蝇侵染率和昆虫负载量，主要是优势物种的，随着植物物种和功能群丰富度的增加而降低。这些影响在盆栽植物中未观察到，因此可能是由寄主植物性能和质量的变化介导的。寄生率，主要是丰富的小蜂和的寄生率，在移植植物和盆栽植物中都随着植物物种或功能群丰富度的增加而增加，这表明植物多样性的直接影响最为重要。移植植物和盆栽植物中的差异影响强调了植物介导的直接和间接影响对群落水平营养相互作用的重要性。研究结果还表明了植物间相互作用如何严重影响使用移植植物获得的结果。更普遍地说，我们的结果表明植物生物多样性通过多种不同机制影响较高营养级的丰度。
