Trussell Geoffrey C, Ewanchuk Patrick J, Matassa Catherine M
Marine Science Center, Northeastern University, 430 Nahant Road, Nahant, Massachusetts 01908, USA.
Ecology. 2006 Dec;87(12):2979-84. doi: 10.1890/0012-9658(2006)87[2979:tfober]2.0.co;2.
Food chain length is an important property of ecosystems, but the mechanisms maintaining it remain elusive. Classical views suggest that energetic inefficiencies (the "energy-flow hypothesis") limit food chain length, but others have argued that better explanations reside in more complex scenarios that consider the stability of food webs or the combined effects of productivity and ecosystem size. We argue that abandonment of the energy-flow hypothesis is premature. For a simple tritrophic rocky intertidal food chain, we show that the efficiency of energy transfer is strongly influenced by predation risk and consumer density. Effects tied to predation risk were particularly strong, explaining 32% of the variation in growth efficiency (compared to 15% for density effects) and reducing it by 44-76%. Hence, the stress (fear of being eaten) that predators impose on prey may be instrumental in limiting energy transfer up the food chain and thus contribute to the shortening of food chains.
食物链长度是生态系统的一个重要属性，但其维持机制仍不明确。传统观点认为能量低效性（“能量流动假说”）限制了食物链长度，但也有人认为更好的解释存在于更复杂的情形中，这些情形考虑了食物网的稳定性或生产力与生态系统大小的综合影响。我们认为摒弃能量流动假说还为时过早。对于一个简单的三营养级岩石潮间带食物链，我们发现能量转移效率受到捕食风险和消费者密度的强烈影响。与捕食风险相关的影响尤为显著，解释了生长效率变化的32%（相比之下，密度影响为15%），并使其降低了44%-76%。因此，捕食者施加于猎物的压力（对被吃掉的恐惧）可能有助于限制食物链上游的能量转移，从而导致食物链缩短。
