Fisher M C, Viney M E
Division of Biological Sciences, University of Edinburgh, UK.
Proc Biol Sci. 1998 Apr 22;265(1397):703-9. doi: 10.1098/rspb.1998.0350.
We have investigated the population genetic structure of the parasitic nematode Strongyloides ratti in wild rats. In the UK, S. ratti reproduces predominantly by mitotic parthenogenesis, with sexual forms present at a rate of less than 1%. S. ratti was found to be a prevalent parasite and substantial genetic diversity was detected. Most rats were infected with a genotypic mixture of parasites. A hierarchical analysis of the genetic variation found in S. ratti sampled across Britain and Germany showed that 73.3% was explained by variation between parasites within individual hosts and 25.3% by variation between rats within sample sites. Only a small proportion (1.4%) of the total genetic variation was attributable to genetic subdivision between sample sites, suggesting that there is substantial gene flow between these sites. Most parasites sampled were found to exist in Hardy-Weinberg equilibrium and this population genetic structure is discussed in view of the virtual absence of sexual reproduction.
我们研究了野生大鼠体内寄生线虫——鼠类圆线虫的群体遗传结构。在英国，鼠类圆线虫主要通过有丝分裂孤雌生殖进行繁殖，有性生殖形式的出现率低于1%。研究发现鼠类圆线虫是一种常见寄生虫，并且检测到了大量的遗传多样性。大多数大鼠感染的是寄生虫的基因型混合物。对在英国和德国采集的鼠类圆线虫的遗传变异进行的层次分析表明，73.3%的变异可由个体宿主体内寄生虫之间的变异解释，25.3%可由采样地点内大鼠之间的变异解释。总遗传变异中只有一小部分（1.4%）可归因于采样地点之间的遗传细分，这表明这些地点之间存在大量的基因流动。大多数采集到的寄生虫被发现处于哈迪-温伯格平衡状态，鉴于几乎不存在有性生殖，我们对这种群体遗传结构进行了讨论。
