Spatio-temporal variation of species richness and phylogenetic diversity patterns for spring ephemeral plants in northern China

Understanding the spatiotemporal distribution of species diversity in response to climatic change is essential for the conservation and management of species resources. Spring ephemeral plants (SEs) have played a crucial role in sustaining the desert and woodland ecosystems of northern China. However, our knowledge regarding the spatiotemporal variation of species diversity in SEs is limited. In this study, we employed occurrence and phylogenetic data for 200 SEs, alongside 19 environmental variables, to model their geographical distribution during the Last Glacial Maximum (LGM), Current, and the year 2070 (considering two representative concentration pathway scenarios, SSP2-4.5 and SSP5-8.5). We also visualized the phylogenetic diversity patterns in the Current. Our findings revealed that more than half of the SEs notably expanded their range and continuously shifted northeastward from LGM to 2070. From LGM to Current and from Current to SSP2-4.5_2070, 64% and 54% of SEs shifted from higher to lower elevations, and 53% of them will slightly shift to higher elevations from Current to SSP5-8.5_2070. We identified three distinct bioregions corresponding to the core ranges of desert SEs and understory SE ecotypes. The Ili Valley, Tacheng Basin, northern and southern Junggar Basin, and Changbai Mountains were identified as hotspots for species richness, phylogenetic diversity, and endemism for the two SE ecotypes. Notably, these hotspots had limited overlap with existing nature reserves. Additionally, the suitable habitat of desert SEs was primarily determined by precipitation seasonality and precipitation of driest month, whereas the distribution of forest understory SEs was mainly influenced by annual precipitation and temperature seasonality. This study significantly contributes to a comprehensive understanding of the modern diversity distribution patterns and conservation priorities for SEs within a species distribution and phylogenetic framework.