Abstract: To understand the diversity and spatial distribution of benthic macroinvertebrates in the Chaobai River Basin, surveys of macrobenthos in the main rivers were performed in summer (July) and autumn (September) of 2022. The community structure characteristics, diversity features, and niche of dominant species were analyzed. A total of 153 taxonomic units of macrobenthos were identified, with insects as the main dominant group. Baetis sp. and Hydropsyche sp. were the common dominant species in both seasons. The abundance of macrobenthos showed patterns from high to low as north > south, tributary > mainstem, upper-stream and middle-stream > lower-stream. The α-diversity of the benthic community showed no seasonal difference. However, the Shannon index and the richness index had significant geographical variations. The heterogeneity of macrobenthic communities was high among different seasons, and the pattern of β-diversity was dominated by turnover components. Baetis sp. and Hydropsyche sp. had the largest niche breadth in both seasons, occupying a wider resource utilization spectrum. The niche overlap between Polypedilum paraviceps and Tanytarsus chinyensis in summer, between Baetis sp. and Hydropsyche sp. in autumn was the highest, indicating intense interspecific competition. Our results suggested the mountain tributaries of Chaobai River Basin nurtured relatively high macrobenthos diversity, while the community structure of macrobenthos in the urban reaches was relatively single, forming a typical mountainous-urban macrobenthos spatial pattern. This study can provide data basis for related research in the Chaobai River Basin, and facilitate formulating ecological management and biodiversity conservation policies for urban rivers.

Key words: Chaobai River Basin, benthic macroinvertebrate, distribution pattern, biodiversity characteristics, ecological niche