Data from: Geographic variation in hybridisation and ecological differentiation between three syntopic, morphologically similar species of montane lizards

To understand factors shaping species boundaries in closely related taxa, a powerful approach is to compare levels of genetic admixture at multiple points of contact, and determine how this relates to intrinsic and extrinsic factors, such as genetic, morphological and ecological differentiation. In the Australian Alps, the threatened alpine bog skink Pseudemoia cryodroma co-occurs with two morphologically and ecologically similar congeners, P. entrecasteauxii and P. pagenstecheri, and all three species are suspected to hybridise. We predicted that the frequency of hybridisation should be negatively correlated with genetic divergence, morphological differentiation, and microhabitat separation. We tested this hypothesis using a mitochondrial locus, 13 microsatellite loci, morphological and microhabitat data, and compared results across three geographically isolated sites. Despite strong genetic structure between species, we detected hybridisation between all species pairs, including evidence of backcrossed individuals at the two sites where all three species are syntopic. Hybridisation frequencies were not consistently associated with genetic, morphological or ecological differentiation. Furthermore, P. entrecasteauxii and P. pagenstecheri only hybridised at the two sites where they are syntopic with P. cryodroma, but not at the largest site where P. cryodroma was not recorded, suggesting that P. cryodroma may serve as a bridging species. This study reveals the complex dynamics within a three species hybrid zone and provides a baseline for assessing the impact of climate change and anthropogenic habitat modification on future hybridisation frequencies.

为解析近缘类群物种边界的形成因子，一种高效研究策略是对比多个接触位点的遗传渐渗水平，并明确其与遗传、形态及生态分化等内、外源因子的关联。在澳大利亚阿尔卑斯山区，受胁高山泥炭沼石龙子（*Pseudemoia cryodroma*）与两个形态、生态特征相似的同属物种——*P. entrecasteauxii*和*P. pagenstecheri*同域分布，且推测三者均可发生杂交。本研究提出假说：杂交频率应与遗传分化、形态分化及微生境分离程度呈负相关。本研究借助1个线粒体基因座、13个微卫星（microsatellite）基因座、形态及微生境数据对该假说进行验证，并对比了3个地理隔离位点的研究结果。尽管物种间存在显著的遗传结构，本研究仍检测到所有物种对间的杂交事件，且在三个物种同域分布的两个位点发现了回交个体的证据。杂交频率并未与遗传、形态或生态分化呈现稳定的关联模式。此外，*P. entrecasteauxii*与*P. pagenstecheri*仅在与*P. cryodroma*同域分布的两个位点发生杂交，而在未记录到*P. cryodroma*的最大研究位点中未发生杂交，这表明*P. cryodroma*可能充当了杂交桥梁物种。本研究揭示了三物种杂交带内的复杂动态过程，并为评估气候变化与人为生境改造对未来杂交频率的影响提供了基准参照。