Isolation effects and soil properties drive genetic differentiation in Ormosia microphylla populations

The genetic characteristics of six wild populations of Ormosia microphylla were investigated and their soil properties were analyzed by using Hyper-seq sequencing technology. Based on the findings, targeted protection strategies are proposed. Genetic diversity analysis revealed moderate overall genetic diversity of O. microphylla populations, with the ZD showing the highest and the JX the lowest genetic diversity. Compared to the populations outside the tiankeng, the LY, located in a Karst tiankeng, exhibited lower genetic diversity. This reduced genetic diversity of LY was possibly influenced by the combined influence of selective pressures unique to the tiankeng environment as well as the founder effect. Genetic structure analysis further indicated that the optimal number of clusters for the six populations was K = 7. The LY exhibited a relatively pure genetic constitution, whereas the other populations exhibited more complex genetic structures. Phylogenetic analysis and assessments of genetic differentiation coefficients further demonstrated significant genetic distance of the LY from the other populations, with a high degree of differentiation. Overall, there was a significant level of genetic differentiation among the six populations. Soil analysis revealed that total organic content and Fe were significantly higher compared to other elements across the six populations. In addition, compared to other populations, the LY exhibited notable variations in soil characteristics, such as higher levels of Fe, K, TK, and Ca. Additionally, the pH of the soil harboring LY was neutral, whereas that of other populations was acidic. IBD analysis, after removing the LY, revealed that the outcomes changed from non-significant to significant, highlighting the critical role of the isolation effect of Karst tiankeng and geographical barriers in promoting genetic differentiation among populations. IBE analysis further indicated a significant impact of K and TK content in the soil on genetic differentiation between populations.