New data on the taxonomy, systematics, and phylogeny of the tribe Boreoheptagyiini Brundin (Diptera: Chironomidae: Diamesinae)

A multilocus phylogeny of the tribe Boreoheptagyiini was reconstructed using nuclear (18S, 28S, and CAD4) and mitochondrial (COI5P, COI3P, and COII) genes. Species delimitation using ASAP analysis of DNA barcodes identified 22 molecular operational taxonomic units (mOTUs), which were congruent with morphological species hypotheses. Based on robust phylogenetic and morphological evidence, we formally propose the transfer of the genus Sasayusurika Makarchenko, including S. nigatana (Tokunaga), from the tribe Diamesini to the tribe Boreoheptagyiini. To maintain monophyly, the genera Palatovia Makarchenko et Semenchenko and Kaluginia Makarchenko are downgraded to subgeneric rank within the genus Boreoheptagyia Brundin. Furthermore, Boreoheptagyia kurobebrevis (Sasa et Okazawa, 1992) and B. unica Makarchenko were reclassified to the subgenus Kaluginia Makarchenko, and B. zhengi Lin et Liu, 2021 to the subgenus Shilovia Makarchenko. In this regard, the new structure of the Boreoheptagyiini tribe with all its taxa, their diagnosis based on morphological data, keys, descriptions, and redescriptions for adult males as well as for immature stages of the studied species, are presented. In this revision, two new species, Boreoheptagyia (s. str.) elbursica sp. nov. and B. (s. str.) serratosioi sp. nov. are also described. These taxonomic revisions provide a more stable and phylogenetically consistent classification for the Boreoheptagyiini tribe.