Integrative Taxonomy Reshapes Palaearctic–Oriental Biogeography: First Discovery of Dicranomyia (Sivalimnobia) (Diptera, Limoniidae) in Mainland China with Two New Species

The crane fly subgenus Sivalimnobia has been taxonomically stagnant for over half a century, with its apparent absence from mainland China representing a major biogeographic anomaly. We address this by integrating detailed morphology and COI DNA barcoding of specimens collected across 14 Chinese provinces. Our study conclusively establishes the presence of Sivalimnobia in mainland China, resolving three species: the newly recorded and continentally widespread Dicranomyia (Sivalimnobia) alticola Edwards, 1916, and two new endemic species—D. (S.) bispinosa sp. nov. (restricted to Yunnan) and D. (S.) inflata sp. nov. (a cryptic lineage within the D. (S.) alticola complex distributed across Chongqing, Sichuan and Yunnan). The discovery of D. (S.) inflata sp. nov. was validated by a discrete male genitalic autapomorphy and a pronounced COI barcode gap (8.7–9.6% divergence). These findings update the global biogeography of the subgenus, identifying India as the primary diversity center and southwestern China as a significant secondary center. The overall pattern suggests a “stepping-stone dispersal and multi-center diversification” model. This work transforms Sivalimnobia from a taxonomic relic into a model for studying Eurasian insect biogeography and highlights the conservation importance of East Asian montane stream habitats.