Assessment of Genetic Diversity and Genetic Structure of Saussurea medusa (Asteraceae), a “Sky Island” Plant in the Qinghai–Tibet Plateau, Using SRAP Markers

Saussurea medusa Maxim. is a typical “sky island” species and one with the highest altitude distributions among flowering plants. The present study aimed at analyzing the genetic diversity and population structure of 300 S. medusa accessions collected from 20 populations in the Qilian Mountains in the northeastern Qinghai–Tibet Plateau (QTP), using sequence-related amplified polymorphism (SRAP) markers. A total of 14 SRAP primer combinations were employed to analyze genetic diversity and population structure across all accessions. Out of 511 amplified bands, 496 (97.06%) were polymorphic. The populations in the eastern Qilian Mountains had significantly higher genetic diversity than those in the central and western groups. Population structure analysis revealed greater genetic differentiation among populations with a Gst of 0.4926. UPGMA-based clustering classified the 300 S. medusa accessions into 3 major clusters, while the Bayesian STRUCTURE analysis categorized them into 2 groups. Correlation analyses showed that the genetic affinity of the populations was based on differences in geographical distance, moisture conditions, and photothermal conditions between the habitats. This study represents the first comprehensive genetic assessment of S. medusa and provides important genetic baseline data for the conservation of the species.