Analysis of the distribution pattern of Chinese Ziziphus jujuba under climate change based on optimized biomod2 and MaxEnt models

Ziziphus jujuba has high ecological and economic value and is widely distributed in northern China. Reconstructing the historical geographic distribution patterns of Z. jujuba and determining the environmental distribution restrictions could provide a scientific basis for its germplasm conservation and management. Here, the R packages ENMeval and Biomod2 were used assess to 121 distribution records and 18 environmental variables and model and analyze the geographic distribution changes of Z. jujuba in different periods since the last interglacial period. Environmental anomalies and factors underlying the geographical distribution changes and migration trends in distribution areas under climate change were assessed. The optimized MaxEnt model generated the best predictions, and the modern highly suitable area was located in the Yellow and Haihe river basins. Climate anomalies in the historical periods ranged in decreasing order from the last interglacial > last glacial maximum > middle Holocene. The degree of climate anomalies under RCP (Representative Concentration Pathways) 2.6-2050s was the lowest, and the degree of climate anomalies under RCP8.5-2070s was the highest. From the last interglacial period to the 2070s, the most dissimilar variable was initially precipitation but gradually changed to temperature with climate change, which was the key factor for the geographical distribution of Z. jujuba. Although extensive habitat expansion occurred during the last interglacial period, the area suitable for Z. jujuba retreated to higher latitudes during the last glacial maximum and middle Holocene. As climate warming intensifies, suitable habitats will shift to higher latitudes while habitats in lower latitudes will become scarcer. The whole suitable region in China will migrate to a higher latitude area, indicating that the Z. jujuba distribution shows a strong response to climate change. This study provides a theoretical basis for establishing conservation measures for Z. jujuba genetic resources and studying trends in plant formation and evolution in North China.