Inter-specific connectivity and stability of the unique relic plant Chunia bucklandioides in a community at different structural levels on Hainan Island, China

Introduction Relic plants are crucial components of biodiversity. Studying the interspecific relationships and stability of endangered relic plants at various structural levels within communities helps to understand their survival status and provides a scientific foundation for conserving unique germplasm resources and biodiversity. Methods This study aims to address the following scientific questions: How does species composition across different distribution areas influence interspecific relationships? Which plant species impact the survival of Chunia bucklandioides populations in these areas? Are there differences in community stability at various structural levels? Based on survey data from the mountainous communities of Chunia bucklandioides in the Jianfengling and Di’anshan sections of Hainan Tropical Rainforest National Park, this study uses the variance ratio method (VR), test statistics (W), chi-squared test (χ 2 ), AC connectivity coefficient, percentage co-occurrence (PC) test, and an improved stability analysis method developed by M. Godron to analyze interspecific relationships and community stability at different structural levels. Results The results show that: (1) The communities inhabited by Chunia bucklandioides have rich species composition, and there are significant differences in community structure between the Jianfengling area and the Diaoluoshan area. (2) In both distribution regions, positive interspecific associations dominate among species in different forest layers of the Chunia bucklandioides communities, with strong interspecific association in the arbor layer and weak interspecific association in the shrub layer and herb layer. (3) Different structural layers of the Chunia bucklandioides communities in both the Jianfengling area and the Diaoluoshan area are in an unstable state. In terms of stability, the performance of the two distribution regions is as follows: Diaoluoshan area community > Jianfengling area community; the order is reversed among different forest layers—for the Jianfengling area: arbor layer > shrub layer > herb layer; for the Diaoluoshan area: herb layer > shrub layer > arbor layer. (4) Mature individuals of Chunia bucklandioides occupy an absolute dominant position in the community, while juvenile individuals are under highly competitive pressure, leading to restricted population regeneration. Discussion This research provides valuable insights into the interspecific relationships, community stability, and succession dynamics of endangered Chunia bucklandioides populations, offering key scientific knowledge for their conservation and practical guidance for ecosystem restoration in tropical rainforests.