Species diversity and maintenance mechanisms of benthic macroinvertebrate assemblages in the Xijiang River
Aims:The Xijiang River,renowned for its rich freshwater biodiversity and endemism,presents an intriguing yet understudied ecosystem.This study aims to elucidate the species diversity patterns and underlying mechanisms maintaining macroinvertebrate communities in this mega river.Drawing from published literature and an extensive field survey conducted from 2021 to 2023,our objectives include compiling a comprehensive species checklist,identifying ecological drivers shaping community structure,and proposing conservation strategies.Methods:Macroinvertebrates were sampled from key water bodies within the Xijiang River,including main stream,tributaries,and plateau lakes from the years 2021 to 2023.One-way ANOVA was employed to analyze species diversity indices across different water bodies.PERMANOVA(permutational multivariate analysis of variance)and PCoA(principal co-ordinates analysis)were used to assess community structure variation,while canonical correspondence analysis and variation partitioning identify potential key factors influencing macroinvertebrate community organization.Results:A total of 704 species from 437 genera,representing 150 families across 10 orders and 5 phyla,were documented(combining 506 historical records with 352 findings from 2021 to 2023).The proportion of species endemic to China reaches as high as 26％of the total number of species.The average density and biomass in the present survey period were 437.53 ind./m2 and 38.65 g/m2,respectively.Tanypus sp.,Glyptotendipes sp.,Parafossarulus striatulus and Corbicula fluminea emerged as the dominant species.Species richness and diversity indices were highest in tributaries,followed by the main stream and lakes.Canonical correspondence analysis(CCA)revealed that a combination of environmental factors(e.g.,altitude,conductivity and chemical oxygen demand with permanganate)and spatial factors jointly influenced macroinvertebrate community structure.Moreover,variation partitioning highlighted the dominance of environmental factors in tributaries and lakes,while spatial factors predominantly influenced main stream communities.Conclusion:This study presents the most comprehensive inventory of macroinvertebrates in the Xijiang River to date,showcasing its significance as a global biodiversity hotspot.Despite the region's rich macroinvertebrate biodiversity,anthropogenic pressures have led to a decline in species richness.To safeguard and restore macroinvertebrate diversity and endemism,proactive conservation measures are imperative.Strategies should include curbing overfishing,regulating illicit mining practices,restoring natural hydrological patterns and riparian zones,mitigating point and non-point source pollution,and preventing the encroachment of non-native species.
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