Mithen S J, Lawton J H
Department of Biology, University of York, Y01 5DD, Heslington, York, UK.
Oecologia. 1986 Jul;69(4):542-550. doi: 10.1007/BF00410360.
An approximately constant ratio of number of predator species/number of prey species is observed in several natural communities, although the exact value of the ratio may vary with habitat and the types of organisms in the food web. We test the hypothesis that a constant predator/prey ratio can be generated by what Holt (1977) terms 'apparent competition' and what Jeffries and Lawton (1984) call 'competition for enemy-free space'. We create simple, two trophic-level communities by drawing species of predators and prey at random from a species pool, simulating their interactions using Lotka-Volterra models. The simulated food webs converge over successive periods of invasion and extinction to locally stable systems with approximately constant ratios of number of predator species/number of prey species, despite varying initial conditions. As expected, predator/prey ratios take different values depending upon the 'biology' of the simulated species. We conclude that apparent competition between prey species via shared enemies may be one mechanism whereby approximately constant predator/prey ratios are generated in natural communities.
在几个自然群落中观察到捕食者物种数量与猎物物种数量的比例大致恒定，尽管该比例的确切值可能因栖息地和食物网中生物的类型而异。我们检验了这样一个假设，即恒定的捕食者/猎物比例可以由霍尔特（1977年）所称的“表观竞争”以及杰弗里斯和劳顿（1984年）所说的“对无天敌空间的竞争”产生。我们通过从物种库中随机抽取捕食者和猎物物种，创建简单的两个营养级群落，并使用洛特卡-沃尔泰拉模型模拟它们之间的相互作用。尽管初始条件不同，但模拟的食物网在连续的入侵和灭绝时期后会收敛到局部稳定的系统，其中捕食者物种数量与猎物物种数量的比例大致恒定。正如预期的那样，捕食者/猎物比例因模拟物种的“生物学特性”而异。我们得出结论，猎物物种通过共享天敌之间的表观竞争可能是在自然群落中产生大致恒定的捕食者/猎物比例的一种机制。
