Sophany Phauk: Primary and secondary symbionts: Symbiotic diversity of Auchenorrhyncha (Hemiptera) and their ecological interactions

Abstract

Auchenorrhynchan insects (leafhoppers, planthoppers, and spittlebugs) maintain long-term symbiotic relationships with intracellular bacteria that are essential for their nutrition, development, and ecological success. This research provides the first comprehensive investigation of bacterial symbiont diversity in Cambodian Auchenorrhyncha across 25 insect species from upland habitats of the Central Cardamom Mountains, rice-associated agroecosystem, and host–parasitoid interactions. Using 16S rRNA (V3–V4) Illumina sequencing, bacterial communities were characterized from these auchenorrhynchans. Across all samples, the obligate endosymbiont Candidatus Karelsulcia muelleri dominated, often co-occurring with its co-obligate partner Ca. Nasuia deltocephalinicola in Deltocephalinae leafhoppers and Ca. Zinderia insecticola (of Clovia sp.), forming a conserved dual system essential for amino acid synthesis. Alongside these, diverse secondary symbionts including Arsenophonus, Wolbachia, Rickettsia, Sodalis, Spiroplasma, Ca. Symbiodolus, and Ca. Lariskella were detected. An upland species of Clovia sp. exhibited a greater symbiont diversity, likely reflecting ecological heterogeneity and host-plant variation, while floodplain leafhoppers showed reduced diversity associated with agroecosystem. Symbiont composition was primarily host-specific, with environmental factors playing minor roles, although localized patterns indicated subtle ecological filtering. The detection of shared symbionts between auchenorrhynchans and parasitoids (Dryinidae and Halictophagidae) suggests possible horizontal bacterial transmission through parasitisation. Overall, these studies reveal that Auchenorrhyncha–microbe associations in Cambodia are both evolutionarily stable and ecologically dynamic: obligate symbionts ensure host survival, whereas secondary symbionts enhance adaptability to environmental and biological stressors. These findings provide a foundation for future studies on the functional genomics, transmission dynamics, and applied potential of insect symbionts in tropical ecosystems.