Buckling A, Kassen R, Bell G, Rainey P B
Department of Plant Sciences, University of Oxford, UK.
Nature. 2000;408(6815):961-4. doi: 10.1038/35050080.
External agents of mortality (disturbances) occur over a wide range of scales of space and time, and are believed to have large effects on species diversity. The "intermediate disturbance hypothesis", which proposes maximum diversity at intermediate frequencies of disturbance, has received support from both field and laboratory studies. Coexistence of species at intermediate frequencies of disturbance is thought to require trade-offs between competitive ability and disturbance tolerance, and a metapopulation structure, with disturbance affecting only a few patches at any given time. However, a unimodal relationship can also be generated by global disturbances that affect all patches simultaneously, provided that the environment contains spatial niches to which different species are adapted. Here we report the results of tests of this model using both isogenic and diverse populations of the bacterium Pseudomonas fluorescens. In both cases, a unimodal relationship between diversity and disturbance frequency was generated in heterogeneous, but not in homogeneous, environments. The cause of this relationship is competition among niche-specialist genotypes, which maintains diversity at intermediate disturbance, but not at high or low disturbance. Our results show that disturbance can modulate the effect of spatial heterogeneity on biological diversity in natural environments.
外部死亡因素（干扰）在广泛的时空尺度上发生，并且被认为对物种多样性有很大影响。“中度干扰假说”提出在中等干扰频率下具有最大多样性，这一假说已得到野外和实验室研究的支持。在中等干扰频率下物种的共存被认为需要在竞争能力和干扰耐受性之间进行权衡，并且需要一个集合种群结构，即干扰在任何给定时间仅影响少数斑块。然而，如果环境包含不同物种所适应的空间生态位，那么同时影响所有斑块的全球干扰也能产生单峰关系。在这里，我们报告了使用荧光假单胞菌的同基因种群和多样化种群对该模型进行测试的结果。在这两种情况下，多样性与干扰频率之间的单峰关系是在异质环境中产生的，而不是在同质环境中。这种关系的原因是生态位特化基因型之间的竞争，这种竞争在中等干扰水平维持了多样性，但在高干扰或低干扰水平则不然。我们的结果表明，干扰可以调节自然环境中空间异质性对生物多样性的影响。
