Proper conceptual framework of community assembly is critical for understanding biodiversity patterns. In this work, we raised the concepts, ‘predominant/ assistant trait’, to characterize distinct trait roles in the processes of community organizing. We further incorporated them into previous theoretical understanding. Upon this theoretical basis, we presented a case study with two rodent datasets in the Hengduan Mountains, China. Due to weak phylogenetic signal and extraordinary habitat heterogeneity, we detected most of the rodent communities appeared random at both phylogenetic and morphological facets, which have prevented us to identify the role of morphological attributes and major process structuring rodent communities. We inferred that the variations in trait role, trait conservatism and habitat heterogeneity are major noise confounding our understanding on community assembly. Based on theoretical modification and empirical demonstration, this work has offered a novel and comprehensive perspective to understand the patterns of phylogenetic and trait-based community structure.