Gram-Negative Bacteria Across Spatial Scales: A Meta-Analysis of Ant-Associated Bacterial Communities Under Distinct Environmental Conditions.

Shaped by ecological and evolutionary factors, microbial communities influence host health and resistance to environmental stressors. Ants that host diverse bacterial communities may rely on these communities for adaptation to different environmental conditions. This meta-analysis investigates the proportion of Gram-negative (GN) bacteria in ants' bacterial communities (gut and whole body) under contrasting environments at distinct scales: (i) arboreal vs. ground habitats and (ii) tropical vs. temperate zones. We hypothesize that ants under greater environmental variability (arboreal and in temperate zones) host higher proportions of GN bacteria, which are better suited to extreme ecological pressures. We analyzed data from 193 ant bacterial communities across 27 studies and found that ants from temperate regions and arboreal microhabitats do harbor higher proportions of GN bacteria compared to those from tropical regions or ground microhabitats. This suggests that GN bacteria may confer adaptive advantages in variable environments, potentially enhancing host resistance to stressors. Our findings underscore the role of abiotic ecological factors in shaping ant-associated bacterial communities and highlight the need for further research on how GN bacteria contribute to insect survival in less stable environments. Future studies should explore the functional roles of GN bacteria in host resistance, particularly regarding climate change and ecosystem disruptions.