Concentrated conservation and utilization: Four medicinal crops for diabetes treatment showed similar habitat distribution patterns in China

Revealing the potential geographical distribution and regions that yield maximum harvest of products will be of great significance for evaluation and utilization of crops in medicinal industry. Diabetes has become a global health problem that threatens almost all nations in the world. The traditional Chinese medicine (TCM) has long been used for the treatment of diabetes in history. Specifically, four medicinal plants including huangqi (Astragalus membranaceus [Fisch.] Bunge.), huanglian (Coptis chinensis Franch.), shengdi (Rehmannia glutinosa [Gaetn.] Libosch. ex Fisch. et Mey.), and xuanshen (Scrophularia ningpoensis Hemsl.) have been confirmed effective in diabetes treatment with clear anti-diabetic mechanisms. In recent years, increasing demand of pharmaceutical industry as well as human activities lead to the degradation of habitat and drop in production of the four species. A pressing problem faced by scientists is how to propose effective conservation and utilization strategies of these medicinal crops. In this study, a comprehensive evaluation on the potential geographical distribution of the four medicinal crops was conducted based on the maximum entropy (Maxent) modeling. A total of 227, 426, 433, and 353 localities for A. membranaceus, C. chinensis, R. glutinosa, and S. ningpoensis, respectively, in China were used as the occurrence data. Ten bioclimatic variables were used as environmental factors. The results showed that the Maxent modeling generated high area under curve (AUC) values of 0.947, 0.966, 0.959, and 0.959, respectively. The areas of suitable distribution for the four species are 878,181 km(2), 684,406 km(2), 768,132 km(2), 714,267 km(2), respectively. The main decisive environmental factors that determine the potential distribution are bio12, bio12, bio6, and bio6, respectively. By further determining the core distribution regions and main producing provinces of the four species, it was found that A. membranaceus and R. glutinosa shared similar potential habitats which mainly located in northern China, while C. chinensis and S. ningpoensis shared similar potential habitats which mainly located in South and Central China. Furthermore, the former two species have similar suitable precipitation condition, while the latter two species have similar suitable precipitation condition. These results thus raised the possibility of conducting concentrated conservation and utilization of the four species in overlapping distribution regions to obtain the maximum products for pharmaceutical industry. Collectively, these results will provide valuable references for the conservation and utilization of the four medicinal crops as well as other endangered species.