Abstract:

Aims: Chironomidae are widely recognized as important bioindicators in freshwater ecosystems. However, their highly conservative morphology limits the effectiveness of traditional taxonomic approaches for reliable species identification. The Xiaomyiini, an oriental lineage within Chironominae, remains poorly understood in terms of species diversity and distribution patterns. 

Methods: A total of 100 mitochondrial cytochrome c oxidase subunit I (COI) barcode sequences were generated from specimens collected across multiple regions in China. Molecular species delimitation was conducted using Neighbor-Joining (NJ) phylogenetic analysis and the Automatic Barcode Gap Discovery (ABGD) method. Ecological niche analyses were performed based on climatic and topographic variables, and a random forest model was employed to identify key environmental drivers of intergeneric differentiation. 

Results: The COI barcode exhibited high discriminatory power within Xiaomyiini. The ABGD analysis consistently recovered 10 molecular operational taxonomic units, exceeding the number of currently recognized morphological species and indicating substantial cryptic diversity. Niche analyses revealed overall niche conservatism within Xiaomyiini, while Xiaomyia and Shangomyia differed in environmental space utilization. Random forest results highlighted temperature-related variables, particularly the mean temperature of the wettest quarter, along with elevation, as primary drivers of ecological differentiation. 

Conclusion: This study provides new molecular evidence for species delimitation within Xiaomyiini and highlights the presence of considerable cryptic diversity. The findings contribute to a better understanding of ecological differentiation within the tribe and offer baseline data for improving the DNA barcode reference database of Chironomidae.

Key words: COI, Xiaomyia, Shangomyia, species delimitation