Survival at the edge: genomic vulnerability and genetic purging of a limestone cliff-endemic sky island shrub under climate change

: 2.24e-3 to 2.80e-3), high differentiation (average fixation index: 0.16), drastic historical decline, and strong genetic load among populations. Notably, the northeasternmost and most recently diverged population (Jiankou) exhibited extreme inbreeding but the lowest genetic load, suggesting that genetic purging enhances small population survival. The genotype-environment association analysis identified 1,286 core SNPs potentially correlated with local adaptation. Genomic offset projections predicted high maladaptation risk under future climates, especially in eastern and southern populations. This study provides essential insights into the mechanisms of local adaptation, genomic vulnerability, and climate resilience of threatened sky island species, and offers guidance for targeted conservation strategies.