Waves of range dynamics and gene flow characterize the biogeographic history of Litsea elongata , a dominant tree in East Asian evergreen broadleaved forests

Societal Impact Statement Evergreen broadleaved forests (EBLFs) represent an iconic vegetation type in subtropical montane East Asia, but they are experiencing intensifying anthropogenic pressure and increasing habitat fragmentation. Here, using a dominant and widespread tree species characteristic of East Asian EBLFs, we examine its phylogeographic history and evaluate what it implies about connectivity via gene flow among subtropical montane forests. We found that the montane EBLFs of East Asia, presently disjunct, may have been extensively connected in the past. This work advances our understanding of the biogeography of East Asian EBLFs and provides evidence relevant to their conservation and management. Summary Evergreen broadleaved forests (EBLFs) are widely distributed across montane regions of subtropical East Asia, but the evolutionary histories of their dominant species remain poorly understood. Here, we combine phylogenetic, population genetic, biogeographical, and fossil evidence to investigate the biogeographic history of Litsea elongata , a dominant and widespread tree in East Asian EBLFs. We identified distinct geographic clades of L. elongata and determined that present patterns of genetic diversity have been shaped by past waves of range expansion, gene flow, and range contraction. Two distinct clades co‐occur sympatrically in the Himalaya‐Hengduan Mountains, one of which experienced gene flow with a disjunct karst‐specialized clade in southwest China. We also detected ancient gene flow between this karst clade and a clade in eastern China, presently separated by over 800 km. The geographic range of L. elongata has been historically dynamic and suggests that the dominant tree of EBLFs had more extensive ancient connections across distinct montane regions in subtropical East Asia than previously recognized.