Abstract: Watershed-scale aquatic biodiversity and its spatiotemporal variations represent a pivotal focus in ecosystem research and aquatic biodiversity conservation.This study investigated the diversity patterns (species and phylogenetic dimensions) of benthic macroinvertebrate communities within the Beipan River,a tributary of the Pearl River Basin,through watershed-scale monitoring.A total of 39 taxonomic units of benthic macroinvertebrates were identified,spanning 3 phyla,6 classes,14 orders,28 families,and 39 genera.From the perspective of species diversity,the species richness,Shannon-wiener index,Pielou's evenness index,and Simpson dominance index of benthic macroinvertebrates were 39.00,2.60,0.71 and 9.24,respectively.From the perspective of phylogenetic diversity,the taxonomic diversity index,taxonomic distinctness index,average taxonomic distinctness index,and variation in taxonomic distinctness index were 49.07,55.18,69.34,and 631.74,respectively.Notably,β-diversity partitioning highlighted contrasting drivers:species β-diversity was predominantly shaped by turnover processes (73%),whereas phylogenetic β-diversity was governed by nestedness components (65%).BioEnv method was used to analyze the relationship between the two dimensions of beta diversity and their components with environmental distances,and the results indicated that elevation was a key factor determining the species and phylogenetic β-diversity patterns of the benthic macroinvertebrate communities.This study provides critical baseline data and theoretical underpinnings for biodiversity conservation strategies in the Pearl River Basin and the construction of the ecological barrier in Southwest China.