Potential impacts of climate change on the distribution of the relict plant Shaniodendron subaequale

Shaniodendron subeaqualis is a tertiary relict plant unique to China. This species has high greening, ecological, and scientific research value, and has been listed as a national I-level key protected plant. Clarifying the main climatic factors restricting the geographical distribution of S. subeaqualis and predicting the potential geographical distribution pattern of this species can provide a scientific basis for the protection of the germplasm resources of this rare species. Based on 104 S. subeaqualis natural distribution records and 9 climate factors, the MaxEnt software was used to predict the potential suitable areas of S. subeaqualis in different periods (LGM, MH, Current, SSP245-2050s, SSP245-2090s, SSP585-2050s, SSP585-2090s). The results showed that the contemporary AUC predicted by MaxEnt is 0.996, with high simulation accuracy; Precipitation in the driest season (Bio17), the average temperature in the coldest season (Bio11) are main factors affecting the distribution of S. subeaqualis. At present, the suitable area of S. subeaqualis is mainly distributed in Jiangsu, Anhui, and Zhejiang province, with a total area of 11.575 × 104 km2, of which the high suitable area is 1.424 × 104 km2 and the medium suitable area is 3.826 × 104 km2. In the LGM, the area of S. subeaqualis was roughly similar to that of the contemporary period, but there was a southward migration phenomenon in some areas, such as the suitable area in the south of Zhejiang. In order to avoid the influence of ice age, S. subeaqualis moved to nearby refuge places, such as Dabie Mountain area of Anhui province, the west of Tianmu Mountain area of Zhejiang province and mountain area of Jiangsu province. In the MH, the suitable area for S. subeaqualis was reduced and moved northward to a small extent. In the future period, the suitable range of S. subeaqualis will not change greatly, but the overall degree of fragmentation will intensify. If effective measures are not taken, it is bound to bring severe challenges to the survival of S. subeaqualis. In order to protect S. subeaqualis germplasm resources more effectively, it is suggested to dynamically monitor the existing S. subeaqualis population and take various measures actively to reduce the negative effects of climate change on S. subeaqualis.