Data from: Geographical isolation and environmental heterogeneity contribute to the spatial genetic patterns of Quercus kerrii (Fagaceae)

Southwest China is one of the major global biodiversity hotspots. The Tanaka line, extending within southwestern China from its northwest to its southeast, is an important biogeographical boundary between the Sino-Japanese and Sino-Himalayan floristic regions. Understanding the evolutionary history of the regional keystone species would assist with both reconstructing historical vegetation dynamics and ongoing biodiversity management. In this research, we combined phylogeographic methodologies and species distribution models (SDMs) to investigate the spatial genetic patterns and distribution dynamics of Quercus kerrii, a dominant evergreen oak inhabiting southwest China lowland evergreen broadleaved forests (EBLFs). A total of 403 individuals were sampled from 44 populations throughout southwest China. SDMs and mismatch distribution analysis indicated that Q. kerrii has undergone northward expansion since the Last Glacial Maximum (LGM). Quantitative analysis revealed that the range expansion of Q. kerrii since the LGM exceeded that of the sympatric mid-elevation species Quercus schottkyana, likely owing to their contrasting distribution elevations and habitat availabilities. The historical climate change since the LGM and the latitude gradient of the region played an important role in shaping the genetic diversity of Q. kerrii. The genetic differentiation index and genetic distance surface of Q. kerrii populations east of the Tanaka line exceeded those to its west. The long-term geographic isolation and environmental heterogeneity between the two sides of the Tanaka line might increase species divergence patterns and local adaptation. This study provides new insights into the historical dynamics of subtropical EBLFs and the changing biota of southwest China.

中国西南地区是全球主要的生物多样性热点区域之一。田中线（Tanaka line）自中国西南地区的西北向东南延伸，是分隔中日植物区系与喜马拉雅植物区系的重要生物地理界线。解析区域关键物种的演化历史，有助于重建历史植被动态并推进当前的生物多样性管理工作。本研究结合系统发育地理学方法与物种分布模型（species distribution models, SDMs），对栖息于中国西南低地常绿阔叶林（lowland evergreen broadleaved forests, EBLFs）的优势常绿栎类物种柯氏栎（Quercus kerrii）的空间遗传格局与分布动态展开探究。研究团队在中国西南全境共布设44个种群，采集了总计403个个体样本。物种分布模型与错配分布分析结果表明，柯氏栎自末次冰盛期（Last Glacial Maximum, LGM）以来经历了向北扩张过程。定量分析显示，柯氏栎自末次冰盛期以来的分布范围扩张幅度超过了同域分布的中海拔物种Quercus schottkyana，这一差异可能源于二者在分布海拔与栖息地可获得性上的显著分化。自末次冰盛期以来的历史气候变化与该区域的纬度梯度，对柯氏栎的遗传多样性塑造发挥了重要作用。田中线以东的柯氏栎种群的遗传分化指数与遗传距离表面均高于西侧种群。田中线两侧长期存在的地理隔离与环境异质性，可能加剧了物种分化格局与本地适应进程。本研究为亚热带常绿阔叶林的历史动态以及中国西南地区生物区系的变化提供了全新的研究视角。