Rheum nanum, a perennial herb, is a famous traditional Chinese medicinal plant that has great value in modern medicine. In order to determine the potential distribution of R. nanum in Asia, we specifically developed the potential distribution maps for three periods (current, 2050s: 2041–2060, and 2070s: 2061–2080) using MaxEnt and ArcGIS, and these were based on the current and future climate data under two climate scenarios (RCP2.6 and RCP6.0). To predict the potential impacts of global warming, we measured the area of suitable habitats, habitat suitability changes, and habitat core changes. We found that bio16 (i.e., the precipitation of the wettest quarter) and bio1 (i.e., the annual mean temperature) were the most important climate factors that influenced the distribution of R. nanum. The areas of high suitable habitats (HH) and middle suitable habitats (MH) in the current period were 156,284.7 ± 0.99 km² and 361,875.0 ± 3.61 km², respectively. The areas of HH and MH in 2070RCP6.0 were 27,309.0 ± 0.35 km² and 123,750 ± 2.36 km², respectively. The ranges of 82.0–90.3° E, 43.8–46.5° N were the mostly degraded areas of the 2050s and 2070s, and RCP6.0 had a larger decrease in habitable area than that found in RCP2.6. All the HH cores shifted south, and the shift distance of HH in 2070RCP6.0 was 115.65 km. This study provides a feasible approach for efficiently utilizing low-number occurrences, and presents an important attempt at predicting the potential distribution of species based on a small sample size. This may improve our understanding of the impacts of global warming on plant distribution and could be useful for relevant agricultural decision-making.

The Loess Plateau, known for its fragile ecosystems, is one of the traditional apple-producing regions in China. Although some management measures are needed to enhance sustainable agriculture in response to the rising pressure of climate change, the geographic distribution of apple trees considering multiple variables has not been considered. In this study, we used three software (the maximum entropy model, IDRISI, and ArcGIS) to simulate the potential distribution of suitable habitats and range shifts of apple trees in the near present and near future (i.e., the 2030s and the 2050s) under two climate scenarios (the Shared Socioeconomic Pathways (SSP)1-26 and SSP5-85), while taking a variety of environmental factors into account (e.g., temperature, precipitation, and terrain). After optimization, the class unsuitable habitat (CUH) changed the potential distribution pattern of apple trees on the Loess Plateau. Currently, the areas of lowly suitable habitat (LSH), moderately suitable habitat (MSH), highly suitable habitat (HSH), and CUH were 7.66 × 10⁴, 2.80 × 10⁴, 0.23 × 10⁴, and 18.05 × 10⁴ km², respectively. Compared to the centroid estimated under the climate of 1970–2000, the suitability range of apple trees was displaced to the northwest in both the 2030s and the 2050s in SSP5-85 (i.e., 63.88~81.30 km), causing a larger displacement in distance than SSP1-26 (i.e., 40.05~50.32 km). This study demonstrates the possible changes in the spatial distribution of apple trees on the Loess Plateau in the near future and may provide a strong basis for future policy making.

Germplasm resources are an important basis for genetic breeding, and the study of genetic diversity is beneficial to the discovery and improvement of germplasm resources. In this study, 132 local germplasm of sweet potato were used as test materials, and 20 phenotypic traits were analyzed for genetic diversity using distribution frequency, coefficient of variation, and Shannon's diversity index; carotenoid contents in sweet potato tubers were measured by HPLC, and their genetic diversity was analyzed using the coefficient of variation, mean, and standard deviation. Meanwhile, the genetic diversity, as well as population structure, were analyzed based on 10 pairs of SSR molecular markers using Nei's genetic diversity index and Shannon's diversity index. The results showed that the 132 sweet potato landraces had high genetic diversity based on phenotypic traits, SSR molecular markers, and carotenoid content, respectively; based on population structure analysis, the 132 sweet potato landraces could be divided into five subgroups. Analysis of molecular variation (AMOVA) showed that 84% of the variation existed within populations and 16% between populations. This study provides a basis for the selection of parental material for the genetic breeding improvement of sweet potato and for the mining of superior genes.