Effects of environmental factors on genetic diversity in the endangered <i>Notopterygium incisum</i> from the southeastern Qinghai–Tibetan Plateau

Abstract Notopterygium incisum is an endangered medicinal plant species endemic to China, primarily distributed in the eastern peripheral regions of the Qinghai–Tibetan Plateau. As a widely utilized medicinal plant, N. incisum faces increasing threats from environmental changes and anthropogenic disturbances, which are altering its biological habitats and elevating its risk of extinction. These challenges pose significant obstacles to the species' breeding and conservation. To inform more effective breeding strategies and conservation measures, this study investigated the genetic diversity, population differentiation, and evolutionary history of N. incisum , as well as the environmental influences on 343 individuals from 38 natural populations, using 15 ISSR markers. The results reveal a moderate level of genetic diversity across the sampled populations. The 38 populations were grouped into two major clusters derived from a common ancestor. Genetic diversity was found to be correlated with altitude, latitude, and average annual temperature, and pop35 and pop27 exhibited the highest genetic diversity indices, representing valuable genetic germplasm for breeding programs. These populations may serve as excellent parental lines to improve breeding efficiency and success. Notably, populations located in Aba, Sichuan Province, at altitudes between 2500 and 3800 m and latitudes of 32–33°N, showed higher genetic diversity, suggesting stronger adaptive capacity in these environments. This finding provides a theoretical basis for selecting experimental sites for future breeding efforts. For conservation, in situ strategies are recommended for populations with high genetic diversity. Those under significant environmental threat may benefit from ex situ conservation, such as seed or rhizome collection, to maximize genetic representation.