Dispersal predicts hybrid zone widths across animal diversity: Implications for species borders under incomplete reproductive isolation

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. Lastly, the data suggest that dispersal and molecular divergence set lower bounds on hybrid zone widths in animals, indicating 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.

Methods
These data were culled from a meta-analysis of over 150 studies of 131 hybrid zone systems.

Also included are the scripts available on GitHub, zipped for archival purposes: https://github.com/singhal/hz_metaanalysis

诸多动物类群的分布范围边界常以杂交带（hybrid zone）的形式出现。关于杂交带的形成与稳定机制，其中一类经典模型为张力区模型（tension zone model），该模型的核心预测为：杂交带的宽度由随机扩散进入杂交带的过程与针对杂种的选择压力之间的动态平衡所决定。本研究旨在探究：随机扩散以及针对杂种选择的替代指标（即杂交类群间的遗传距离），能否解释131个动物杂交类群对的杂交带宽度差异。研究结果表明，仅这两类因素即可解释动物杂交带宽度约40%的变异，且随机扩散对变异的解释度远高于遗传距离。不同进化枝（clade）内的模式存在特异性：爬行动物类群中，遗传距离对杂交带宽度的预测效果尤为显著；而在鸟类类群中，该关系与张力区模型的预测结果恰好相反。此外，数据显示随机扩散与分子分化共同限定了动物杂交带宽度的下限，表明杂交带的形成存在地理限制条件。综上，本研究进一步证实了随机扩散在杂交带形成过程中的核心重要性，以及其在更广范围的分布边界生态学中的关键作用。

方法
本数据集源自针对131个杂交带系统的150余项研究的荟萃分析。

本数据集还包含为存档目的压缩的GitHub开源脚本，仓库地址为：https://github.com/singhal/hz_metaanalysis