Abstract: To elucidate the relationship between the population size of dominant thrips species on different host plants and altitude, we examined the altitudinal distribution patterns of dominant thrips at elevations ranging from 1800 to 3200 m in the Dashanbao Nature Reserve, Zhaotong City, Yunnan Province. Regression analysis, correlation analysis, and significance testing were applied to explore the effects of altitude and host plants on the distribution patterns of dominant thrips species. The results showed that the dominant thrips populations were mainly composed of Frankliniella occidentalis (an invasive species) and Haplothrips chinensis (a native species). The population size of F. occidentalis on Trifolium repens (r=-0.889, P<0.001), Aster oliganthus (r=-0.822, P=0.001), and Buddleja davidii (r=-0.487, P=0.065) decreased, whereas population size of F. occidentalis on Anaphalis margaritacea (r=0.533, P=0.032) significantly increased with increasing altitude. The population of H. chinensis declined with increasing altitude on T. repens (r=-0.770, P<0.001), increased on B. davidii (r=0.123, P=0.661) and A. margaritacea (r=0.419, P=0.005), and was not observed on A. oliganthus. The population of F. occidentalis at 3200 m showed no significant difference compared to those at 1800, 2150, and 2500 m, while significant differences were observed among all other altitude pairs (P<0.05). For H. chinensis, the highest abundance occurred at 1800 m; the population at an altitude of 2500 m was also significantly higher than that at 2150 m (P<0.05), with no significant differences among other altitudes. F. occidentalis and H. chinensis were the dominant thrips species in Dashanbao Nature Reserve, with F. occidentalis being more abundant than H. chinensis. Across the altitudinal gradient from 1800 m to 3200 m, the invasive species F. occidentalis exhibited a continuous decline in population with increasing elevation, whereas the native species H. chinensis showed a tendency to aggregate toward higher altitudes, with relatively higher abundance in these regions.

Key words: Dashanbao Nature Reserve, Frankliniella occidentalis, dominant species, altitude gradient, host plant