From genes to ecosystems: Analyzing Ormosia microphylla endangerment driven by multiple dimensions

Background The ecologically and economically important species Ormosia microphylla faces a high extinction risk. However, systematic studies on the multiple threats faced by these populations and mechanisms underlying the interactions among threats remain limited. To formulate effective conservation strategies, we conducted population surveys across seven natural populations within its main distribution range. Results Overall, 71% of the studied populations exhibited unstable age structures. Population genomic analyses classified the populations into three genetic clusters that were all characterized by low genetic diversity. The slowest decline rate was predicted for the HN (individuals from Tongdao and Cengbu; lacking young individuals) cluster than for the GX (individuals from Nandan) and HG (individuals from Jianhe, Liping, Jingzhou, and Tangbaocun; lacking mature trees or dominated by senescent individuals) clusters. However, the GX cluster possessed a more stable age structure. Selective sweep analysis further revealed enhanced fatty acid biosynthesis and metabolism pathways in the GX cluster. Further, saplings predominated within the HG cluster. Although all populations produced viable seeds, seed production declined annually and germination was restricted by the seed coat. Illegal logging (tree stumps) evidence was observed in all populations, with populations exhibiting more stumps having fewer mature adult trees. Finally, soil nutrients were not significantly correlation with seedling number, whereas bird diversity was positively correlated with seedling numbers. Conclusions These results help reconcile the apparent contradictions between field observations and genetic predictions and highlight the critical importance of curbing illegal logging and monitoring bird diversity for the recovery and persistence of O. microphylla populations.