Poulin Robert
Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand.
Int J Parasitol. 2006 Jul;36(8):877-85. doi: 10.1016/j.ijpara.2006.02.021. Epub 2006 Mar 29.
Within any parasite species, variation among populations in standard infection parameters (prevalence, intensity and abundance) is an accepted fact. The proportion of hosts infected and the mean number of parasites per host are not fixed values across the entire geographic range of any parasite species. The question is whether this inter-population variation occurs within a narrow, species-specific range and is thus driven mainly by the biological features of the parasite, or whether it is substantial and unpredictable, leaving population parameters at the mercy of local conditions. Here, the repeatability of estimates of prevalence, intensity and abundance of infection was assessed across populations of the same parasite species, for 77 metazoan parasite species of Canadian freshwater fishes. Overall, parameter values from different populations of the same parasite species were more similar to each other and more different from those of other species, than expected by chance alone. Much of the variation in parameter values in the dataset was associated with differences between parasite species, rather than with differences among populations within species. This was particularly true for intensity and abundance of infection; in contrast, prevalence values, while somewhat repeatable among populations of the same species, still showed considerable variation. Among the higher taxa investigated (monogeneans, trematodes, cestodes, nematodes, acanthocephalans, copepods), there was no evidence that species of one taxon display intrinsically greater variation in population parameters than species of other taxa. Overall, the results suggest that intensity and abundance of infection are real species characters, though somewhat variable. This conclusion supports the view that the biological features of parasite species can potentially override local environmental conditions in driving parasite population dynamics.
在任何寄生虫物种中，种群之间在标准感染参数（流行率、感染强度和丰度）方面存在差异是一个公认的事实。在任何寄生虫物种的整个地理分布范围内，被感染宿主的比例和每个宿主体内寄生虫的平均数量都不是固定值。问题在于，这种种群间的差异是发生在一个狭窄的、物种特异性的范围内，因此主要由寄生虫的生物学特征驱动，还是差异很大且不可预测，使得种群参数受当地条件的摆布。在此，针对加拿大淡水鱼的77种后生动物寄生虫物种，评估了同一寄生虫物种不同种群间感染流行率、感染强度和丰度估计值的可重复性。总体而言，同一寄生虫物种不同种群的参数值彼此之间比单独随机预期的更为相似，且与其他物种的参数值差异更大。数据集中参数值的大部分变异与寄生虫物种之间的差异有关，而非物种内种群之间的差异。对于感染强度和丰度而言尤其如此；相比之下，流行率值虽然在同一物种的种群间有一定的可重复性，但仍表现出相当大的变异。在所研究的较高分类单元（单殖吸虫、吸虫、绦虫、线虫、棘头虫、桡足类）中，没有证据表明一个分类单元的物种在种群参数上比其他分类单元的物种表现出本质上更大的变异。总体而言，结果表明感染强度和丰度是真实的物种特征，尽管存在一定变异性。这一结论支持了这样一种观点，即寄生虫物种的生物学特征在驱动寄生虫种群动态方面可能会超越当地环境条件。
