Bohannan Brendan J M, Lenski Richard E
Am Nat. 1999 Jan;153(1):73-82. doi: 10.1086/303151.
We demonstrated that the presence of invulnerable prey can result in a shift in the balance between top-down and bottom-up control of a model food chain. Our model food chain consisted of the bacterium Escherichia coli and the bacteriophage T4 (a virus that feeds on E. coli) in chemostats supplied with different concentrations of glucose. The E. coli population consisted of individuals that were susceptible to predation by T4 ("edible" E. coli) and individuals that were resistant to predation by T4 ("inedible" E. coli). The equilibrium density of a heterogeneous prey population (consisting of edible and inedible E. coli) increased strongly in response to an enrichment of its resources. This response consisted of an increase in the inedible fraction of the prey population but no change in the edible fraction. In contrast, a homogeneous prey population (edible E. coli only) increased only marginally. The equilibrium density of the predator population (bacteriophage T4) did not significantly increase in response to enrichment when its prey were heterogeneous, but it increased strongly when its prey were homogeneous.
我们证明，存在不易受攻击的猎物会导致模型食物链中自上而下和自下而上控制之间的平衡发生转变。我们的模型食物链由大肠杆菌和噬菌体T4（一种以大肠杆菌为食的病毒）组成，它们存在于供应不同浓度葡萄糖的恒化器中。大肠杆菌群体由易受T4捕食的个体（“可食用”大肠杆菌）和对T4捕食具有抗性的个体（“不可食用”大肠杆菌）组成。异质猎物种群（由可食用和不可食用的大肠杆菌组成）的平衡密度随着资源的富集而显著增加。这种反应包括猎物种群中不可食用部分的增加，但可食用部分没有变化。相比之下，同质猎物种群（仅可食用大肠杆菌）仅略有增加。当猎物是异质时，捕食者种群（噬菌体T4）的平衡密度对富集没有显著增加，但当猎物是同质时，它会显著增加。
