Abstract: Taking the Morus alba thicket community on Pingtan Island as the study subject, this research analyzes population niche breadth characteristics and classifies species into specialized and generalist types. It investigates niche breadth traits at the population level and their response to environmental conditions. Results indicate: The Dodonaea viscosa shrub community exhibits high species richness, with 161 species recorded. Among these, The Dodonaea viscosa possesses the highest mean importance value (32.58%) and ecological niche width (26.06). The number of specialized species (2,340) exceeded that of generalized species (1,313) in both the shrub and herb layers, with their classification largely consistent with niche breadth rankings. This distinction was influenced by differences in mean importance values and niche breadth rankings. Boruta feature selection identified 8 and 9 environmental factors affecting population niche breadth in the shrub and herb layers, respectively, with soil organic matter (SOM) ranking highest in importance. Principal component analysis indicated that the distribution range of population-level environmental factors narrowed successively among specialized, neutral, and generalized species, with no significant preferences for specific environmental factors across different groups; Structural equation modeling results revealed that altitude (AL), available phosphorus (AP), and soil organic matter were key factors. Topographic factors primarily influenced population niche breadth indirectly through soil factors, and population niche breadth showed a positive correlation with resource abundance.