Geographic differentiation of the gut microbiota in Lissorhoptrus oryzophilus (Coleoptera: Curculionidae): associations with environmental gradients and predicted functional potential.

The rice water weevil, Lissorhoptrus oryzophilus (Kuschel), is a major invasive pest native to rice that has expanded far beyond its native North American range to establish widespread populations across Asia and Europe. However, how altitudinal gradients shape this microbial ecosystem remains unclear. We performed shotgun metagenomics to profile the gut microbiota of 3 geographically distinct populations-Pingba District (PB), Yibin City (SC), and Mudanjiang (MDJ) City-of L. oryzophilus across elevational gradients in China. Though low-abundance archaeal, fungal, and viral sequences were detected, bacterial taxa (>89% of annotated genes) dominated functional profiles. All populations were Proteobacteria-dominated, but PB was enriched in Erwiniaceae (Pantoea deleyi), while SC/MDJ were dominated by Rickettsiaceae (Rickettsia/Wolbachia). Population-specific taxa were most abundant in MDJ (19 species), followed by PB (15), with SC harboring only 1 unique species. Predicted functional profiles aligned with taxonomy: PB showed elevated amino acid/carbohydrate metabolism, carbohydrate-active enzyme, and efflux pump gene abundances. SC and MDJ shared similar functional profiles. Principal coordinates analysis revealed distinct clustering of PB across taxonomic and functional dimensions, while SC/MDJ partially overlapped. These correlative findings suggest microbial metabolic plasticity may support the weevil's persistence across heterogeneous environments, though causal links require experimental validation.