Genetic Limitation and Conservation Implications in Tetracentron sinense: SNP-Based Analysis of Spatial Genetic Structure and Gene Flow.

The present research investigates the fine-scale spatial genetic structure (SGS) and gene flow dynamics in the endangered relict tree Tetracentron sinense, a keystone species in China's montane ecosystems facing severe habitat fragmentation and genetic erosion. Utilizing genome-wide SNPs from 378 individuals across four natural populations (BMXS, MGFD, GLGS, SXFP), derived from ddRAD-seq, we quantified genetic diversity, SGS (Sp statistic), and dispersal patterns through spatial autocorrelation, parentage analysis, and age-class stratification. Results indicated critically low heterozygosity (observed heterozygosity, HO = 0.019-0.022) and high inbreeding coefficient (Fis = 0.147-0.304), with moderate SGS (Sp = 0.0076-0.021) suggesting restricted gene flow (effective dispersal radius: 11-32 m). Seed-mediated dispersal was predominant, but topography and rainfall constrained dispersal (<5% beyond 50 m). Saplings exhibited stronger SGS, and the SXFP population experienced 100% sapling mortality due to inbreeding depression. Conservation efforts should prioritize assisted gene flow, habitat restoration, and ex situ sampling at distances greater than 115 m to preserve genetic diversity and adaptive potential. This study highlights the urgent need for genomics-informed conservation strategies in fragmented montane ecosystems.