Large-Scale Sampling Reveals the Strain-Level Diversity of Burkholderia Symbionts in Riptortus pedestris and R. linearis (Hemiptera: Alydidae)

<i>Burkholderia</i> (sensu lato) is a diverse group of β-Proteobacteria that exists worldwide in various environments. The SBE clade of this group was thought to be mutualistic with stinkbugs. <i>Riptortus-Burkholderia</i> was suggested as an ideal model system for studying insect-microbe symbiosis. To explore the strain-level diversity of <i>Burkholderia</i> at the individual and population levels of <i>Riptortus</i> stinkbugs (Hemiptera: Alydidae), and to uncover the factors affecting the <i>Burkholderia</i> community, large-scale sampling of two <i>Riptortus</i> species and deep sequencing data (16S amplicon) were used in the present study. Our results showed that: (1) the proportions of facultative symbiotic bacteria <i>Burkholderia</i> were very high, with an average proportion of 87.1% in the samples; (2) only six out of 1373 <i>Burkholderia</i> amplicon sequence variants (ASVs) did not belong to the SBE clade, accounting for only 0.03% of <i>Burkholderia</i>; (3) a relatively small number of <i>Burkholderia</i> ASVs had a large number of sequences, with 22, 54, and 107 ASVs accounting for more than 1.0%, 0.1%, and 0.01% of the total <i>Burkholderia</i> sequences, respectively; (4) multiple <i>Burkholderia</i> ASVs were present in most <i>Riptortus</i> individuals, but there was one dominant or two codominant ASVs, and codominance was more likely to occur when the genetic distance between the two codominant ASVs was small; and (5) the beta diversity of <i>Burkholderia</i> was significantly different between the two host species (PerMANOVA: both Jaccard and Bray-Curtis, <i>p</i> < 0.001) and among localities (PerMANOVA: both Jaccard and Bray-Curtis, <i>p</i> < 0.001). Two-way PerMANOVA also indicated that both the host (Bray-Curtis, <i>p</i> = 0.020; Jaccard, <i>p</i> = 0.001) and geographical location (Bray-Curtis, <i>p</i> = 0.041; Jaccard, <i>p</i> = 0.045) influence <i>Burkholderia</i> communities; furthermore, Mantel tests showed that the <i>Burkholderia</i> communities were significantly correlated with the geographical distance of sample locations (R = 0.056, <i>p</i> = 0.001). Together, our findings demonstrate the fine-scale diversity of <i>Burkholderia</i> symbionts and suggest a region- and host-dependent pattern of <i>Burkholderia</i> in <i>Riptortus</i> stinkbugs.