Echelle Anthony A, Connor Patrick J
Zoology Department, Oklahoma State University, Stillwater, OK, 74078.
Evolution. 1989 Jul;43(4):717-727. doi: 10.1111/j.1558-5646.1989.tb05171.x.
Apparently between 1980 and 1984, Cyprinodon variegatus was introduced into an area of the Pecos River in Texas, where it hybridized with an endemic species, C. pecosensis. Protein electrophoresis indicated that, by 1985, panmictic admixtures of these two pupfishes occupied approximately 430 river-kilometers of the Pecos River, roughly one-half of the historic range of the endemic species. The average frequency of introduced alleles at four diagnostic loci ranged from 0.18 to 0.84 at the 15 sites sampled from the Pecos River in Texas. Clinal patterns in allele frequencies suggest that C. variegatus was introduced into a mid-reach of the river and that this was followed by both upstream and downstream dispersal of the introduced alleles. All pairwise combinations of loci showed significant linkage disequilibrium. The level of disequilibrium indicates chromosomal linkage for one gene-pair, Gpi-A and Est-1. The change in pupfish allele frequencies in the Pecos River represents an extreme example of rapid natural selection in a seminatural situation.
显然，在1980年至1984年期间，德州豹鳉被引入到德克萨斯州佩科斯河的一个区域，在那里它与当地物种佩科斯鳉杂交。蛋白质电泳表明，到1985年，这两种鳉鱼的随机交配混合群体占据了佩科斯河约430公里的河道，大约是当地物种历史分布范围的一半。在从德克萨斯州佩科斯河采样的15个位点上，四个诊断位点上引入等位基因的平均频率在0.18至0.84之间。等位基因频率的渐变模式表明，德州豹鳉被引入到河流的中游区域，随后引入的等位基因向上游和下游扩散。所有位点的两两组合都显示出显著的连锁不平衡。不平衡水平表明一对基因Gpi-A和Est-1存在染色体连锁。佩科斯河鳉鱼等位基因频率的变化代表了半自然环境中快速自然选择的一个极端例子。
