Table 3_Large−scale SSR fingerprinting resolves taxonomic distinction between Picea purpurea and Picea asperata and reveals elevation−linked diversity in Qinghai Province, China.xls

Résumé fourni par la source

Spruce (Picea spp.) are ecologically and economically important conifers. However, species delimitation within the genus remains challenging due to extensive morphological plasticity and interspecific gene flow. In this study, we developed a high-resolution molecular identification system based on 15 fluorescent simple sequence repeat (SSR) markers and applied it to 516 spruce individuals representing 13 natural populations across Qinghai Province, China. The SSR panel demonstrated exceptional discriminatory capacity, with a discrimination power (DP) of 0.9998 and an extremely low probability of identity (PI) of 2.4 × 10-5, enabling accurate individual fingerprinting and germplasm traceability. Population structure analyses, including STRUCTURE, principal coordinate analysis (PCoA), and phylogenetic reconstruction, consistently resolved two highly divergent genetic lineages corresponding to Picea purpurea and P. asperata. These results provide strong molecular support for their taxonomic distinctiveness, as evidenced by substantial genetic differentiation (FST = 0.324–0.453) and limited gene flow (Nm < 0.11). In contrast, populations of P. asperata exhibited low levels of genetic differentiation (FST = 0.004–0.107) and extensive admixture, indicating considerable historical and contemporary gene flow among populations. Notably, we identified a significant negative correlation between expected heterozygosity (He) and elevation (r=−0.67, p = 0.012), revealing an elevation−associated genetic diversity cline in which high−elevation populations harbor significantly reduced genetic diversity, a pattern likely reflecting smaller effective population sizes and historical demographic bottlenecks at higher altitudes. This finding underscores the utility of SSR markers in detecting environmentally associated patterns of genetic variation: despite being selectively neutral, their high polymorphism and genome−wide distribution, combined with extensive sampling (516 individuals) across a broad elevational gradient (2,120–3,600 m), provided sufficient resolution to reveal this ecologically meaningful cline. Overall, this study establishes a robust SSR-based fingerprinting framework for spruce germplasm identification and management, resolves longstanding taxonomic uncertainty between P. purpurea and P. asperata, and provides novel insights into elevation-associated genetic variation. These findings have important implications for conservation prioritization, germplasm resource management, and the development of climate-resilient forest management strategies in the Qinghai–Tibet Plateau region.

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