Complex evolutionary dynamics of <i>Sichuana</i> , an endemic katydid genus in the Hengduan Mountains illuminated by mitochondrial phylogenomics and morphological evidence

The Hengduan Mountains (HDM), a biodiversity hotspot in Southwest China, harbour numerous endemic taxa whose diversification has been driven by the complex geological history of this region. This study investigates the diversification of the katydid genus Sichuana, endemic to the HDM, integrating mitochondrial genomics, morphology and biogeography. We sequenced complete mitochondrial genomes of all known geographic populations of Sichuana, revealing four major clades diverging during the Late Miocene (5.06-8.37 Ma). Orogeny-driven vicariance fragmented ancestral populations, while unstable barriers may facilitate mitochondrial introgression, as evidenced by paraphyletic lineages contrasting with distinct morphologies. We describe five new species (S. brevicerca sp. nov., S. fortidens sp. nov., S. qiuzhi sp. nov., S. luqiaoensis sp. nov. and S. pseudomagna sp. nov.) and two subspecies (S. pseudomagna pseudomagna subsp. nov. and S. pseudomagna borealis subsp. nov.), highlighting the taxonomic challenges posed by discordance between mitochondrial DNA-based phylogenies and morphological classifications. This study demonstrates that orogeny-driven vicariance dominates speciation in low-dispersal insects, but transient gene flow complicates species delimitation. Our findings advocate for integrative taxonomy in biodiversity hotspots and highlight the HDM as a model system for studying biogeographic complexity.