Interspecific associations and niche characteristics of communities invaded by Decalobanthus boisianus

Decalobanthus boisianus is a noxious weed that has seriously damaged tropical forest ecosystems on Hainan Island due to its rapid dispersal and growth abilities. We investigated 48 communities invaded by D. boisianus and explored the interspecific associations between the community species using χ tests, association coefficient (AC), percentage of co-occurrence (PC), and the Ochiai and Dice indices. We assessed community stability using the variance ratio (VR) and contribution law method, and examined niche width, niche similarity and niche overlap of D. boisianus and companion species. Results showed that there were 156 companion species in the D. boisianus communities, belonging to Euphorbiaceae, Rubiaceae, Moraceae, Sapindaceae and Lauraceae. There were positive associations between dominant species. The coordinate (44.53, 55.47) between the inverse accumulative percentage of species and their accumulative relative frequency was far from the stability point (20, 80). This indicates that these communities are in an unstable state. Machilus suaveolens, Litsea variabilis, Garcinia oblongifolia, Elaeocarpus dubius, Schefflera octophylla and Aporusa dioica were closely associated with D. boisianus, indicating that these species have •研究报告• © 生 物多 样性 Bio dive rsity Sci enc e 第 4 期 江焕等: 金钟藤入侵群落的种间联结及生态位特征 389 研 究 报 告 similar resource requirements. Decalobanthus boisianus had the highest niche width which overlapped greatly with companion species. The niches among companion species seldomly overlapped. Our results suggest that the invasion of D. boisianus led to an unstable community with intense competition between companion species and D. boisianus. Our findings can be helpful in species selection for biologically controlling to D. boisianus in tropical areas.