Fox Jennifer A, Dybdahl Mark F, Jokela Jukka, Lively Curtis M
Department of Biology, Indiana University, Bloomington, Indiana, 47405.
Laboratory of Ecological Zoology, University of Turku, FIN-20500, Finland.
Evolution. 1996 Aug;50(4):1541-1548. doi: 10.1111/j.1558-5646.1996.tb03926.x.
We examined clonal diversity and the distribution of both clonal and sexual genotypes in a single population of freshwater snails (Potamopyrgus antipodarum) in which diploid sexual individuals and triploid parthenogens coexist. A genetic analysis of individuals from three habitat zones in Lake Alexandrina, New Zealand revealed extremely high clonal diversity: 165 genotypes among 605 clonal individuals. The frequency of triploid clonal individuals increased with increasing depth in the lake, and most of the individual clones were habitat specific, suggesting that differences among habitats are important in structuring the clonal subpopulation. There were also high levels of clonal diversity within habitats, suggesting frequent origins of habitat-specific clones. In contrast, diploid sexual individuals were proportionately more common in the shallow regions of the lake (where infection by trematode larvae is highest), and there was no significant spatial structure in the sexual subpopulation. We suggest that habitat specialization by clones, as well as parasite-mediated selection against common clones, are important factors affecting the structure of this mixed population of sexual and clonal snails.
我们研究了淡水蜗牛（新西兰泥蜗）单一群体中克隆多样性以及克隆和有性基因型的分布情况，该群体中存在二倍体有性个体和三倍体孤雌生殖个体。对来自新西兰亚历山德里纳湖三个栖息地区域的个体进行的遗传分析显示出极高的克隆多样性：在605个克隆个体中存在165种基因型。三倍体克隆个体的频率随着湖泊深度的增加而上升，并且大多数个体克隆具有栖息地特异性，这表明栖息地之间的差异对于构建克隆亚群体很重要。栖息地内部也存在高水平的克隆多样性，这表明具有栖息地特异性的克隆频繁出现。相比之下，二倍体有性个体在湖泊较浅区域（吸虫幼虫感染率最高的地方）比例上更为常见，并且有性子群体中没有明显的空间结构。我们认为，克隆的栖息地特化以及寄生虫介导对常见克隆的选择，是影响这种有性和克隆蜗牛混合群体结构的重要因素。
