Bacterial and Fungal Midgut Communities of Four Australian Citrus Stinkbug Species, With a Focus on Pantoea ‐Like Symbionts and Their Fitness Effects in

ABSTRACT

True bugs harbour diverse microbial symbionts and are models of host–microbe interactions. Yet, most studies focus on bacterial partners of Holarctic‐Oriental species, leaving bacterial and fungal communities of Australasian taxa unexplored. We conducted the first comparative analysis of bacterial and fungal microbiota inhabiting the crypt‐bearing midgut region of Australian stink bugs by focussing on citrus‐associated Biprorulus bibax and Poecilometis strigatus (Pentatomidae), and Lyramorpha rosea and Musgraveia sulciventris (Tessaratomidae). Using high‐throughput amplicon sequencing, we found consistently low‐diversity bacterial communities dominated by host‐specific gammaproteobacterial symbionts within the Pantoea – Erwinia complex, although L. rosea and P. strigatus also harboured several other low‐abundance taxa. Fungal amplicon sequencing recovered low abundance taxa and unevenly represented communities, including Cladosporium , Eremothecium and unassigned Ascomycota, suggesting they were mostly environmentally acquired rather than conserved fungal associates. Despite host specificity, bacterial symbiont phylogeny was incongruent with host phylogeny, indicating host switches and decoupled host‐symbiont evolution. Egg‐surface sterilisation in B. bibax revealed vertical transmission of its dominant Pantoea ‐like symbiont via egg smearing, and its role in host fitness, with aposymbiotic offspring showing reduced survival, delayed development, shorter longevity and lower fecundity. Overall, our findings extend established patterns of stink bug symbiosis to understudied Australian taxa, providing new insights into host–microbe associations, particularly for Tessaratomidae.