Habitat-driven variation in gut microbiome composition and function of the pygmy grasshopper (Tetrix japonica) across diverse ecosystems in China

BACKGROUND: The gut microbiome plays an important role in insect adaptation, yet how habitat variation shapes microbial communities in pygmy grasshoppers remains unclear. We investigated this question using Tetrix japonica, which inhabits diverse ecosystems across China and provides an ideal model to study microbiome-environment interactions. Shotgun metagenomic sequencing was performed on gut samples from six populations representing coniferous forest, broadleaf forests in Shandong and Shaanxi, grassland, shrubland, and laboratory-reared populations. RESULTS: Microbial diversity and community composition varied significantly among habitats, with field populations exhibiting higher diversity than laboratory-reared ones. Despite environmental differences, a core microbiome comprising 1,162 shared species was consistently detected, suggesting stable symbiotic relationships. Habitat-specific microbial signatures were most evident between forest and grassland populations, with lignocellulose-degrading taxa enriched in forest habitats. Moreover, geographic separation between Shandong and Shaanxi broadleaf forests led to distinct microbial profiles despite similar vegetation. Functional analysis revealed differential enrichment of genes related to plant polymer degradation, nitrogen cycling, and secondary metabolite biosynthesis across habitats. CONCLUSION: These findings demonstrate that both habitat conditions and geography influence gut microbiome assembly in T. japonica, with microbiome plasticity facilitating adaptation. The reduced diversity observed in laboratory populations highlights the importance of natural habitats for maintaining functional microbiome integrity.