Late Pleistocene glacial expansion of a low-latitude species Magnolia insignis: Megafossil evidence and species distribution modeling

The Pleistocene Epoch, marked by significant climatic fluctuations and glaciations, profoundly impacted plant populations. However, our understanding of the influences of last glaciations on tropical-subtropical flora and vegetation remains limited due to insufficient data. Here, we present mummified wood of Magnolia insignis (Wall.) Bl. from the Upper Pleistocene (33-30 ka cal. BP) of Maoming, South China, providing direct evidence of a broader historical range for this species during the period prior to the LGM in the last glaciation. Combining these findings with results from MaxEnt modeling, we demonstrate an expanded range of M. insignis into lower latitudes during last glaciation with subsequent interglacial contraction. This represents the second documented case of such a scenario for a cold-tolerant high-elevation plant species at low latitudes. The results of MaxEnt modeling and a comparison of climatic data across different time periods indicate that the contraction of M. insignis from the Maoming and other low latitude regions of East Asia was driven by the increase in summer temperatures during Holocene. This study not only sheds light on the responses of cold-adapted mountainous species at low latitudes of East Asia to last glaciation, but also justifies the importance of their protection in the view of nowadays and future climate changes.