Pfisterer Andrea B, Diemer Matthias, Schmid Bernhard
Institut für Umweltwissenschaften, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
Oecologia. 2003 Apr;135(2):234-41. doi: 10.1007/s00442-002-1169-0. Epub 2003 Feb 14.
Species loss of primary producers is likely to affect processes on other trophic levels. We studied consumption and individual performance of the generalist herbivore Parapleurus alliaceus (Orthoptera) in relation to the species richness of primary producers. Adult grasshoppers were caged and left to feed for 2 weeks on experimental grassland communities ranging in plant species richness from one, two, four, eight to 32 species. Low plant diversity had a negative effect on both plant community biomass and on biomass gain of female grasshoppers, feeding to produce eggs (male grasshoppers did not gain biomass during the feeding period). This was surprising because plots with high plant diversity had a low proportion of grass biomass and grasshoppers preferentially selected grasses, leading to a greater exploitation of grasses in experimental communities of higher diversity. Thus, the concurrent increase in non-grass species in the diet from these high-diversity communities must have been beneficial to the generalist herbivore. In addition to the positive effects of plant diversity, the presence of legumes in a mixture with grasses further enhanced the biomass gain of grasshoppers at a given level of diversity. These findings suggest that plant species loss may lead to shifts in herbivore population sizes, reducing those of generalists and benefiting specialists of the remaining plant species. Our results further suggest that generalist herbivores, by having feeding preferences, can also change the relative abundances of plant species with different functional characteristics. This may feedback on both composition and diversity of plant communities.
初级生产者的物种丧失可能会影响其他营养级的过程。我们研究了多食性食草动物蒜黄腹蝗（直翅目）的取食情况和个体表现与初级生产者物种丰富度之间的关系。将成年蝗虫关在笼子里，让它们在植物物种丰富度从1种、2种、4种、8种到32种不等的实验性草地群落中取食2周。低植物多样性对植物群落生物量和以产蛋为目的取食的雌性蝗虫的生物量增加均有负面影响（雄性蝗虫在取食期内生物量没有增加）。这很令人惊讶，因为植物多样性高的样地中禾本科植物生物量比例较低，而蝗虫优先选择禾本科植物，这导致在多样性较高的实验群落中对禾本科植物的利用率更高。因此，来自这些高多样性群落的食物中，非禾本科物种的同时增加一定对这种多食性食草动物有益。除了植物多样性的积极影响外，豆科植物与禾本科植物混合存在，在给定的多样性水平下进一步提高了蝗虫的生物量增加。这些发现表明，植物物种丧失可能导致食草动物种群数量的变化，减少多食性动物的数量，而使剩余植物物种的专食性动物受益。我们的结果还表明，多食性食草动物由于有取食偏好，也可以改变具有不同功能特征的植物物种的相对丰度。这可能会对植物群落的组成和多样性产生反馈作用。
