Species diversity of environmentally-transmitted bacteria colonizing Riptortus pedestris (Hemiptera: Alydidae) and symbiotic effects of the most dominant bacteria

Riptortus pedestris (Hemiptera: Alydidae) establish endosymbiosis with bacteria in soil where R. pedestris are exposed to extremely diverse microbiota. To better understand ecology and evolution of the symbiosis, it is important to characterize bacterial species diversity colonizing R. pedestris and evaluate their symbiotic effects. Nonetheless, previous research was limited to a model species, Caballeronia insecticola , when investigating the interactions between two groups. In this study, second-instar nymphs were provided with field soil and reared to adult. Then, bacteria colonizing the midguts of R. pedestris were analyzed for species identification based on 16S rRNA. First, a total of 15 bacterial species were detected belonging to Burkholderiaceae. Most R. pedestris were found to harbor single bacterial species, and the insects harbored at most two bacterial species simultaneously. Among R. pedestris harboring single bacterial species, 91.2% harbored genus Caballeronia . The most dominant species was Caballeronia jiangsuensis , not previously documented for symbiotic associations with R. pedestris . Second, in laboratory conditions, the most dominant species, C. jiangsuensis, significantly enhanced the development, body size, and reproductive potentials of R. pedestris , compared to individuals with no symbiotic bacteria. These results add novel information to address how evolutionary and ecological associations have been shaped in the symbiosis.