Hybrid zones occur as range boundaries for many animal taxa. One model for how hybrid zones form and stabilize is the tension zone model, a version of which predicts that hybrid zone widths are determined by a balance between random dispersal into hybrid zones and selection against hybrids. Here, we examine whether random dispersal and proxies for selection against hybrids (genetic distances between hybridizing pairs) can explain variation in hybrid zone widths across 131 hybridizing pairs of animals. We show that these factors alone can explain ∼40% of the variation in zone width among animal hybrid zones, with dispersal explaining far more of the variation than genetic distances. Patterns within clades were idiosyncratic. Genetic distances predicted hybrid zone widths particularly well for reptiles, while this relationship was opposite tension zone predictions in birds. Last, the data suggest that dispersal and molecular divergence set lower bounds on hybrid zone widths in animals, indicating that there are geographic restrictions on hybrid zone formation. Overall, our analyses reinforce the fundamental importance of dispersal in hybrid zone formation and more generally in the ecology of range boundaries.

中文翻译：

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分散预测整个动物多样性的杂种区域宽度：对不完全生殖隔离下物种边界的影响。

杂种区是许多动物类群的范围边界。关于混合区如何形成和稳定的一个模型是拉伸区模型，该模型的一个版本预测混合区的宽度由随机分散到混合区和选择混合区之间的平衡确定。在这里，我们检查了随机分散和针对杂种选择的代理（杂种对之间的遗传距离）是否可以解释131个杂种对中杂种区域宽度的变化。我们表明，仅这些因素就可以解释动物杂种区域之间约40％的区域宽度变化，而散布可以解释的变化远大于遗传距离。进化枝内的模式是特异的。遗传距离对爬行动物的杂种区域宽度预测特别好，而这种关系与鸟类对张力区的预测相反。最后，数据表明分散和分子差异为动物的杂种区宽度设置了下限，表明杂种区形成受到地理限制。总体而言，我们的分析加强了混合在混合带形成中以及更广泛地在范围边界生态学中的基本重要性。