Department of ZoologyUniversity of British ColumbiaVancouver, British Columbia, Canada; Centre for Aquaculture and Environmental ResearchFisheries and Oceans CanadaWest Vancouver, British Columbia, Canada.
Department of Zoology University of British Columbia Vancouver, British Columbia, Canada.
R Soc Open Sci. 2015 Dec 9;2(12):150285. doi: 10.1098/rsos.150285. eCollection 2015 Dec.
The genetic structure of a hybrid zone can provide insights into the relative roles of the various factors that maintain the zone. Here, we use a multilocus approach to characterize a hybrid zone between two subspecies of killifish (Fundulus heteroclitus, Walbaum 1792) found along the Atlantic coast of North America. We first analysed clinal variation along the Atlantic coast using a single-nucleotide polymorphism in the mitochondrial DNA (mtDNA) displacement loop (D-loop) and a panel of nine nuclear microsatellite markers. A model constraining all clines to the same width and centre was not significantly different from a model in which the clines were allowed to vary independently. Locus-by-locus analysis indicated that the majority of nuclear clines shared the same centre as the mtDNA cline, and the widths of these clines were also narrower than that predicted by a neutral model, suggesting that selection is operating to maintain the hybrid zone. However, two of the nuclear clines had widths greater than the neutral prediction and had centres that were displaced relative to the mtDNA cline centre. We also found that a marsh located near the centre of the mtDNA cline demonstrated a bimodal distribution of nuclear hybrid index values, suggesting a deficit of first-generation hybrids and backcrossed genotypes. Thus, selection against hybrid genotypes may be playing a role in maintaining this hybrid zone and the associated steep nuclear and mtDNA clines.
杂种区的遗传结构可以提供有关维持该区域的各种因素的相对作用的见解。在这里，我们使用多位点方法来描述在北美洲大西洋沿岸发现的两种丽鱼（Fundulus heteroclitus，Walbaum 1792）亚种之间的杂种区。我们首先使用线粒体 DNA（mtDNA）置换环（D-环）中的单个核苷酸多态性和九个核微卫星标记的面板分析了大西洋沿岸的渐变变异。一个限制所有渐变都具有相同宽度和中心的模型与一个允许渐变独立变化的模型没有显着差异。逐基因座分析表明，大多数核渐变与 mtDNA 渐变具有相同的中心，并且这些渐变的宽度也比中性模型预测的要窄，这表明选择正在发挥作用以维持杂种区。然而，两个核渐变的宽度大于中性预测值，并且中心相对于 mtDNA 渐变中心发生了位移。我们还发现，位于 mtDNA 渐变中心附近的沼泽显示出核杂种指数值的双峰分布，表明第一代杂种和回交基因型的缺乏。因此，对杂种基因型的选择可能在维持这种杂种区和相关的陡峭核和 mtDNA 渐变中起着作用。
