Wilson J Bastow
Botany Department, University of Otago, P.O. Box 56, Dunedin, New Zealand.
Oecologia. 1996 Apr;106(2):272-276. doi: 10.1007/BF00328608.
Apparent constancy in the ratio of predator species to prey species has been offered as evidence that ecological communities are structured by interspecific interactions. If significantly different from random expectation, this effect would be one of the few sound pieces of evidence for community structure. The evidence was re-evaluated by using the data from previous studies to form species pools, and forming simulated 'communities' by drawing species at random from these pools (with replacement). Using a correlation coefficient (number of predator species versus number of prey species), and also the statistic used by the original workers (where different), the observed predator:prey correlation was compared to that for the random communities. In five studies, the observed predator:prey ratio was not significantly different from random expectation. In the only two studies where there was significant departure from the null model, it was with more variation in the ratio than expected on a random basis. It is concluded that there is as yet no evidence for near-constant predator:prey ratios.
捕食者物种与猎物物种的比例明显恒定，这被视为生态群落由种间相互作用构建的证据。如果与随机预期有显著差异，这种效应将是群落结构为数不多的可靠证据之一。通过使用先前研究的数据形成物种库，并从这些库中随机抽取物种（可重复抽取）来形成模拟“群落”，对该证据进行了重新评估。使用相关系数（捕食者物种数量与猎物物种数量），以及原始研究人员使用的统计量（如有不同），将观察到的捕食者与猎物的相关性与随机群落的相关性进行比较。在五项研究中，观察到的捕食者与猎物的比例与随机预期没有显著差异。在仅有的两项与零模型有显著偏离的研究中，比例的变化比随机情况下预期的更多。得出的结论是，目前尚无证据表明捕食者与猎物的比例接近恒定。
