Gut microbiome diversity and functional profiles of Culicoides across Sanya, Ruili, and Linyi, China

Biting midges (Culicoides spp.) are vectors of diverse microbes such as viruses, bacteria, protozoa, and nematodes that cause diseases in both wild and domestic animals. Despite their ecological significance and role in disease transmission, the composition and underlying mechanisms shaping the gut microbiota of Culicoides remain poorly characterized.

This study aimed to investigate the composition and functional profiles of the gut microbiota of adult Culicoides collected from three representative cities spanning tropical, subtropical, and temperate climate zones in China.

16S high-throughput sequencing was used to study the microbial composition and function of Culicoides in the three regions. This study further incorporated six environmental factors and seven genetic diversity indices to explore their relationships with the microbial community.

The findings revealed significant variations in the gut microbial composition, dominant species, and diversity of Culicoides across different climate zones. Notable differences were observed in microbial functions related to insect growth, development, and oxidative stress, with Culicoides from the Sanya zone exhibiting a greater abundance of functions and participating in more signaling processes. Environmental factors and host genetic diversity across different habitats collectively shape the composition of the gut microbiota of Culicoides. Structural equation modeling (SEM) revealed that environmental factors exert predominantly direct selective effects on microbial community assembly, whereas host genetic diversity plays a critical indirect regulatory role. These environment-host-microbiota interactions exhibit significant spatial heterogeneity. In low-latitude regions (Sanya), environmental factors mainly manifest direct filtering effects, whereas in ecotone areas (Ruili), environmental pressures indirectly modulate microbial composition by altering host genetic adaptation.

Our findings revealed that Culicoides gut microbiomes exhibit distinct biogeographical divergence, characterized by environment-driven variations in microbial community structure and functional potential. Host genetic adaptation serves as a key mediator and synergistic modulator of these patterns. This tripartite environment-host-microbiome interaction demonstrates clear dependence on geographic gradient.