Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697-2525 USA.
Science. 2010 Mar 26;327(5973):1642-4. doi: 10.1126/science.1184814.
Predators determine herbivore and plant biomass via so-called trophic cascades, and the strength of such effects is influenced by ecosystem productivity. To determine whether evolutionary trade-offs among plant traits influence patterns of trophic control, we manipulated predators and soil fertility and measured impacts of a major herbivore (the aphid Aphis nerii) on 16 milkweed species (Asclepias spp.) in a phylogenetic field experiment. Herbivore density was determined by variation in predation and trade-offs between herbivore resistance and plant growth strategy. Neither herbivore density nor predator effects on herbivores predicted the cascading effects of predators on plant biomass. Instead, cascade strength was strongly and positively associated with milkweed response to soil fertility. Accordingly, contemporary patterns of trophic control are driven by evolutionary convergent trade-offs faced by plants.
掠食者通过所谓的营养级联来决定草食动物和植物的生物量，而这种影响的强度受生态系统生产力的影响。为了确定植物特征之间的进化权衡是否会影响营养级控制的模式，我们操纵了捕食者和土壤肥力，并在系统发育野外实验中测量了主要草食动物（桃蚜）对 16 种乳草物种（Asclepias spp.）的影响。草食动物的密度通过捕食的变化和草食动物抗性与植物生长策略之间的权衡来确定。草食动物密度或捕食者对草食动物的影响都不能预测捕食者对植物生物量的级联效应。相反，级联强度与乳草对土壤肥力的反应呈强烈正相关。因此，当前的营养级控制模式是由植物面临的进化趋同权衡所驱动的。
