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）自中国西南地区西北向东南延伸，是划分中日植物区与喜马拉雅植物区的重要生物地理界线。阐明区域关键物种的演化历史，既能助力重建历史植被动态，也可为当前的生物多样性管理工作提供支撑。本研究结合谱系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阔叶林（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研究。研究团队在中国西南地区全域共采集了44个种群的403份个体样本。物种分布模型与错配分布分析结果显示，柯氏栎自末次盛冰期（Last Glacial Maximum, LGM）以来发生了向北扩张。定量分析表明，柯氏栎自末次盛冰期以来的分布区扩张幅度超过了同域分布的中海拔物种斯氏栎（Quercus schottkyana），这一差异大概率源于二者分布海拔与可利用栖息地的显著差异。末次盛冰期以来的历史气候变化与区域纬度梯度，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曲面均高于其西侧种群。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过程。本研究为亚热带常绿阔叶阔叶林（subtropical EBLFs）的历史动态以及中国西南地区生物群落的演变提供了全新的科学视角。