Trussell Geoffrey C, Ewanchuk Patrick J, Matassa Catherine M
Ecol Lett. 2006 Nov;9(11):1245-52. doi: 10.1111/j.1461-0248.2006.00981.x.
Classical views of trophic cascades emphasize the primacy of consumptive predator effects on prey populations to the transmission of indirect effects [density-mediated indirect interactions (DMIIs)]. However, trophic cascades can also emerge without changes in the density of interacting species because of non-consumptive predator effects on prey traits such as foraging behaviour [trait-mediated indirect interactions (TMIIs)]. Although ecologists appreciate this point, measurements of the relative importance of each indirect predator effect are rare. Experiments with a three-level, rocky shore food chain containing an invasive predatory crab (Carcinus maenas), an intermediate consumer (the snail, Nucella lapillus) and a basal resource (the barnacle, Semibalanus balanoides) revealed that the strength of TMIIs is comparable with, or exceeds, that of DMIIs. Moreover, the sign and strength of each indirect predator effect depends on whether it is measured in risky or refuge habitats. Because habitat shifts are often responsible for the emergence of TMIIs, attention to the sign and strength of these interactions in both habitats will improve our understanding of the link between individual behaviour and community dynamics.
营养级联的传统观点强调消费性捕食者对猎物种群的影响在间接影响[密度介导的间接相互作用（DMIIs）]传递中的首要地位。然而，由于捕食者对猎物特征（如觅食行为）的非消费性影响[性状介导的间接相互作用（TMIIs）]，营养级联也可能在相互作用物种的密度没有变化的情况下出现。尽管生态学家认识到这一点，但对每种间接捕食者效应的相对重要性的测量却很少见。对一个包含入侵性捕食蟹（滨蟹）、中间消费者（海螺）和基础资源（藤壶）的三级岩石海岸食物链进行的实验表明，TMIIs的强度与DMIIs相当，甚至超过DMIIs。此外，每种间接捕食者效应的正负和强度取决于它是在有风险的栖息地还是避难所栖息地中测量的。由于栖息地转移通常是TMIIs出现的原因，关注这两种栖息地中这些相互作用的正负和强度将增进我们对个体行为与群落动态之间联系的理解。
