Poulin Robert
Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand.
Int J Parasitol. 2016 Apr;46(4):275-9. doi: 10.1016/j.ijpara.2015.12.002. Epub 2016 Jan 20.
The species richness of freshwater environments is disproportionately high compared with that of the oceans, given their respective sizes. If diversification rates are higher in freshwaters because they are isolated and heterogeneous, this should apply to parasites as well. Using 14 large datasets comprising 677 species of freshwater and marine fish, the hypothesis that freshwater parasites experience higher rates of diversification than marine ones is tested by contrasting the relative numbers of species per parasite genus between the regional endohelminth faunas of fish in both environments. The relationship between the number of parasite genera and the number of parasite species per host was well described by a power function, in both environments; although the exponent of this function was slightly lower for freshwater parasite faunas than marine ones, the difference was not significant. However, the ratio between the number of parasite species and the number of parasite genera per host species was significantly higher in freshwater fish than in marine ones. These findings suggest fundamental differences between the way parasite faunas diversify in freshwater versus marine habitats, with the independent evolution of conspecific parasite populations in isolated host populations being a more common phenomenon in freshwater environments.
鉴于淡水环境和海洋环境各自的面积大小，淡水环境中的物种丰富度相对其面积而言出奇地高。如果淡水环境中物种多样化速率更高是因为其隔离性和异质性，那么这一点应该也适用于寄生虫。利用14个大型数据集，其中包含677种淡水和海洋鱼类，通过对比两种环境中鱼类的区域内寄生虫区系中每个寄生虫属的物种相对数量，来检验淡水寄生虫比海洋寄生虫具有更高多样化速率这一假设。在两种环境中，寄生虫属的数量与每个宿主的寄生虫物种数量之间的关系都能用幂函数很好地描述；尽管淡水寄生虫区系中该函数的指数略低于海洋寄生虫区系，但差异并不显著。然而，淡水鱼中每个宿主物种的寄生虫物种数量与寄生虫属数量的比值显著高于海洋鱼。这些发现表明，淡水和海洋栖息地中寄生虫区系的多样化方式存在根本差异，在隔离的宿主种群中同种寄生虫种群的独立进化在淡水环境中是更为常见的现象。
