Effects of climatic fluctuations on the fragmented distribution pattern of a Tertiary relict plant, Pseudotaxus chienii (Taxaceae), in subtropical China.

This article focuses on the phylogeographical history, genetic structure, and evolutionary dynamics of *Pseudotaxus chienii*, an ancient and rare conifer endemic to subtropical China. Using chloroplast and nuclear genetic markers alongside ecological niche modelling, the study reveals moderate to high genetic diversity and identifies multiple localized glacial refugia primarily in Zhejiang, Jiangxi, and Guangxi provinces. The genetic structure corresponds to geographical regions shaped by complex topography and precipitation patterns, with incomplete lineage sorting causing discordance between chloroplast and nuclear DNA phylogenies. The findings indicate that pre-Quaternary and Quaternary climatic fluctuations, restricted gene flow, and habitat fragmentation have significantly influenced the species’ demographic history and fragmented distribution, providing insights into plant evolution in subtropical China.