Comparative phylotranscriptomics of four sympatric tetrigids provides implications for convergent evolution and morphological discordance.

backgroundThe classification of pygmy grasshoppers (Orthoptera: Tetrigidae) has historically relied on morphological traits that are prone to homoplasy, leading to persistent taxonomic instability, particularly at the Scelimeninae-Tetriginae subfamily interface. Here, we integrated high-throughput transcriptomic data from four sympatric species—Ergatettix serrifemora, Criotettix damingshanensis, Hedotettix latifemurus, and Hedotettix gracilis—with existing genomic resources, including the previously sequenced Gibbotettix parvipulvillus, to reconstruct a robust phylogenomic framework and investigate the genomic basis of ecological adaptation and phenotypic plasticity.

resultsPhylogenomic analysis based on 1,962 single-copy orthologous groups yielded a fully resolved topology that challenged traditional classifications. Gibbotettix parvipulvillus was robustly recovered within the Scelimeninae clade, identifying its spine-reduced morphology as a secondary adaptation rather than a diagnostic feature of Cladonotinae. Conversely, E. serrifemora was firmly placed within Tetriginae, despite its misleading morpholog. Divergence time estimation indicated that H. latifemurus and H. gracilis split approximately 15.87 million years ago (Mya), confirming their status as distinct species driven by putative gene family expansions related to neural behavior and structural morphogenesis, respectively. Furthermore, formal differential expression analysis of wing morphs revealed a conserved potential metabolic trade-off where the cAMP, calcium, cGMP-PKG, insulin, and endocytosis pathways were enriched.

conclusionsOur study demonstrates that morphological convergence in Tetrigidae frequently masks true evolutionary relationships, necessitating a phylogenomic re-evaluation of subfamily boundaries. We provide the first molecular evidence linking wing loss to a potential shift from aerobic hypertrophy to anaerobic maintenance and stress management strategies. These findings offer new insights into the genomic architecture driving speciation and life-history trade-offs in Tetrigidae.