Prediction of suitable planting areas of Rubia cordifolia in China based on a species distribution model and analysis of specific secondary metabolites

The expansion or reduction of suitable habitats for medicinal plants may result from climate change. There are few reports on the distribution of suitable habitats or potential origins of Rubia cordifolia L., a relatively common herb. However, due to its important pharmacological properties, it is essential that high-quality R. cordifolia can be provided in the future. Therefore, this study combined the biomod2 ensemble platform and the secondary metabolites of R. cordifolia roots to predict its suitable habitats and potential planting areas. Root samples and occurrence data were gathered through fieldwork and public databases. Ultra high-performance liquid chromatography was used to measure the concentrations of two important secondary metabolites in the roots. According to the findings, appropriate habitats covering an area of 2,706,795 km2 were found in various regions, primarily in the eastern and southern parts of China. Under future climate scenarios, suitable habitats shrank inward or expanded outward along the current suitable habitats. Additionally, purpurin was extensively spread, and mollugin was narrowly distributed within the suitable habitats, resulting in dispersed and restricted potential planting areas (893,116 km2). In addition, the precipitation of the wettest month is crucial for distributing suitable habitats and the synthesis of two secondary metabolites. However, there is a risk of losing suitable planting areas for R. cordifolia due to future climate scenarios. Therefore, effective conservation and management measures are urgently needed. In conclusion, the findings of this study may serve as a guide for choosing appropriate planting areas for R. cordifolia.