Dobson A P
Parasitology. 1985 Oct;91 ( Pt 2):317-47. doi: 10.1017/s0031182000057401.
A number of published studies of competition between parasite species are examined and compared. It is suggested that two general levels of interaction are discernible: these correspond to the two levels of competition recognized by workers studying free-living animals and plants: 'exploitation' and 'interference' competition. The former may be defined as the joint utilization of a host species by two or more parasite species, while the latter occurs when antagonistic mechanisms are utilized by one species either to reduce the survival or fecundity of a second species or to displace it from a preferred site of attachment. Data illustrating both levels of interaction are collated from a survey of the published literature and these suggest that interference competition invariably operates asymmetrically. The data are also used to estimate a number of population parameters which are important in determining the impact of competition at the population level. Theoretical models of host-parasite associations for both classes of competition are used to examine the expected patterns of population dynamics that will be exhibited by simple two-species communities of parasites that utilize the same host population. The analysis suggests that the most important factor allowing competing species of parasites to coexist is the statistical distribution of the parasites within the host population. A joint stable equilibrium should be possible if both species are aggregated in their distribution. The size of the parasite burdens at equilibrium is then determined by other life-history parameters such as pathogenicity, rates of resource utilization and antagonistic ability. Comparison of these theoretical expectations with a variety of sets of empirical data forms the basis for a discussion about the importance of competition in natural parasite populations. The models are used to assess quantitatively the potential for using competing parasite species as biological control agents for pathogens of economic or medical importance. The most important criterion for identifying a successful control agent is an ability to infect a high proportion of the host population. If such a parasite species also exhibits an intermediate level of pathology or an efficient ability to utilize shared common resources, antagonistic interactions between the parasite species contribute only secondarily to the success of the control. Competition in parasites is compared with competition in free-living animals and plants. The comparison suggests further experimental tests which may help to assess the importance of competition in determining the structure of more complex parasite-host communities.
本文对已发表的多项寄生虫物种间竞争的研究进行了审视与比较。研究表明，可识别出两种普遍的相互作用水平：这与研究自由生活的动植物的学者所认可的两种竞争水平相对应，即“剥削性”竞争和“干扰性”竞争。前者可定义为两种或更多寄生虫物种对宿主物种的共同利用，而后者则发生在一个物种利用拮抗机制来降低另一个物种的存活率或繁殖力，或者将其从偏好的附着位点驱离之时。通过对已发表文献的调查，整理出了说明这两种相互作用水平的数据，这些数据表明干扰性竞争总是以不对称的方式发生。这些数据还被用于估算一些种群参数，这些参数对于确定种群水平上竞争的影响至关重要。针对这两类竞争的宿主 - 寄生虫关联的理论模型，被用于研究利用同一宿主种群的简单双物种寄生虫群落所展现出的预期种群动态模式。分析表明，使竞争的寄生虫物种得以共存的最重要因素是寄生虫在宿主种群中的统计分布。如果两个物种在分布上都呈聚集状态，那么共同的稳定平衡应该是可能的。此时，平衡状态下寄生虫负荷的大小则由其他生活史参数决定，如致病性、资源利用率和拮抗能力等。将这些理论预期与各种实证数据集进行比较，构成了关于竞争在自然寄生虫种群中的重要性讨论的基础。这些模型被用于定量评估利用竞争的寄生虫物种作为具有经济或医学重要性的病原体的生物控制剂的潜力。识别成功控制剂的最重要标准是能够感染高比例的宿主种群。如果这样的寄生虫物种还表现出中等程度的病理学特征或有效利用共享共同资源的能力，那么寄生虫物种之间的拮抗相互作用对控制成功的贡献仅居其次。将寄生虫中的竞争与自由生活的动植物中的竞争进行了比较。该比较提出了进一步的实验测试，这可能有助于评估竞争在决定更复杂的寄生虫 - 宿主群落结构中的重要性。
