Data from: Strong selection against hybrids maintains a narrow contact zone between morphologically cryptic lineages in a rainforest lizard

Phenotypically cryptic lineages comprise an important yet understudied part of biodiversity; in particular, we have much to learn about how these lineages are formed and maintained. To better understand the evolutionary significance of such lineages, we studied a hybrid zone between two morphologically-cryptic phylogeographic lineages in the rainforest lizard, Lampropholis coggeri. Analyzing a multilocus genetic dataset through cline inference, individual-based methods and population measures of disequilibrium and using simulations to explore our genetic results in context of theoretical expectations, we inferred the processes maintaining this hybrid zone. We find that these lineages meet in a hybrid zone that is narrow (~400 m) relative to inferred dispersal rate. Further, the hybrid zone exhibits substantial genetic disequilibrium and sharply coincident and largely concordant clines. Based on our knowledge about the region's biogeography, the species' natural history, and our simulation results, we suggest that strong selection against hybrids structures this system. As all clines show a relatively narrow range of introgression, we posit that this hybrid zone might not yet be in equilibrium. Nonetheless, our results clearly show that phylogeographic lineages can evolve substantial reproductive isolation without concomitant morphological diversification, suggesting that such lineages can constitute a significant component of evolutionary diversity.

表型隐秘支系（phenotypically cryptic lineages）是生物多样性中一类重要却未得到充分研究的类群；具体而言，学界对这类支系的形成与维持机制仍有诸多待解之处。为深入理解此类支系的进化意义，本研究以雨林蜥蜴科氏光蜥（Lampropholis coggeri）为研究对象，对其两个形态隐秘的系统发育支系间的杂交带（hybrid zone）展开探究。本研究通过渐变群（cline）推断、个体本位分析方法以及群体遗传不平衡测度，对多基因座遗传数据集（multilocus genetic dataset）进行分析，并结合理论预期开展模拟实验以解读所得遗传结果，最终推断出维持该杂交带的关键过程。研究发现，两支系形成的杂交带相较于本研究推断的扩散速率而言极为狭窄，宽度仅约400米。此外，该杂交带存在显著的遗传不平衡（genetic disequilibrium），且各渐变群呈现高度重合与大体一致的分布格局。结合该区域的生物地理学背景、该物种的自然历史特征以及模拟实验结果，本研究认为针对杂交个体的强选择作用塑造了这一系统。鉴于所有渐变群的基因渐渗（introgression）范围均相对狭窄，本研究推测该杂交带可能尚未达到进化平衡状态。尽管如此，本研究结果清晰表明，系统发育支系可在未伴随形态分化的情况下演化出显著的生殖隔离（reproductive isolation），这意味着此类支系可构成进化多样性的重要组成部分。