Childs Michael R, Echelle Anthony A, Dowling Thomas E
Zoology Department, Oklahoma State University, Stillwater, Oklahoma, 74078.
Department of Zoology, Arizona State University, Tempe, Arizona, 85287.
Evolution. 1996 Oct;50(5):2014-2022. doi: 10.1111/j.1558-5646.1996.tb03588.x.
A comparison of allozyme and mtDNA frequencies was used for insight into a situation in the Pecos River, Texas where contact between the endemic pupfish (Cyprinodon pecosensis) and an introduced congener (C. variegatus) has resulted in rapid, geographically extensive genetic introgression. Temporal changes in mean frequencies of diagnostic allozyme markers indicate that the clinal pattern of introduced genetic material (Echelle and Connor 1989) is slowly decreasing in amplitude. Significant rank concordance in diagnostic allele frequencies among sites and across sampling years indicates directional influences upon temporal allele frequency change. These observations are consistent with the theory of gene flow in neutral clines. Levels of introgression indicated by each of four allozyme loci and mtDNA were roughly equivalent. The early history of the hybrid swarm is explained by genetic swamping, possibly mediated by selection for C. variegatus or C. variegatus × C. pecosensis, at a time when the normally abundant endemic species had been catastrophically depleted. High frequencies of an introduced GPI-A allele in all samples of intergrades suggests that the introduced genome originated with a single founding event.
通过比较等位酶和线粒体DNA频率，来深入了解德克萨斯州佩科斯河的一种情况，当地特有鳉鱼（佩科斯鳉，Cyprinodon pecosensis）与引入的同属物种（杂色鳉，C. variegatus）接触后，导致了快速且在地理上广泛的基因渗入。诊断性等位酶标记平均频率的时间变化表明，引入基因物质的渐变群模式（埃谢尔和康纳，1989年）幅度正在缓慢减小。各地点间以及不同采样年份的诊断性等位基因频率存在显著的等级一致性，表明对时间上的等位基因频率变化存在定向影响。这些观察结果与中性渐变群中的基因流理论一致。四个等位酶位点和线粒体DNA所表明的基因渗入水平大致相当。杂交群体的早期历史可以用基因淹没来解释，这可能是在正常数量丰富的特有物种遭受灾难性减少时，由对杂色鳉或杂色鳉×佩科斯鳉的选择介导的。在所有中间类型样本中，引入的GPI - A等位基因频率很高，这表明引入的基因组起源于单一的奠基事件。
