Potential Range Shifts of Two Sympatric <i>Fagus</i> Species

<i>Fagus longipetiolata</i> Seemen and <i>Fagus lucida</i> Rehder & E.H. Wilson are the dominant species in subtropical deciduous broad-leaved forests of China, playing crucial ecological and economic roles. As ecologically and economically important trees, it is critical to understand their responses to climate change. This study employed MaxEnt modeling to discover the range shifts from their historical distributions to future projections. The distribution of suitable habitats of <i>F. longipetiolata</i> is more affected by precipitation, and that of <i>F. lucida</i> is more sensitive to temperature. High-suitability habitats for both species were concentrated predominantly in the Yangtze River Basin. While both species showed substantial distribution centroid shifts since the Last Glacial Maximum (LGM), <i>F. lucida</i> exhibited greater habitat fragmentation and more pronounced reductions in high-suitability areas under projected climate change compared to <i>F. longipetiolata</i>. Our results suggest that despite close phylogenetic relationships, these sister species face divergent climate change threats, with <i>F. lucida</i> being more vulnerable. These findings not only advance the conservation strategies for <i>F. lucida</i> but also provide critical insights for mitigating the impacts of intensifying global warming on subtropical forest ecosystems.