Conservatism and stability of the symbiotic system of the invasive alien treehopper Stictocephala bisonia (Hemiptera,Cicadomorpha, Membracidae)

1. Nutritional symbiosis between insects and microorganisms (bacteria and/or yeast-like symbionts) that provide amino acids and vitamins which are lacking in the diet of host insects is widespread in nature. Auchenorrhyncha are usually host to two ancient bacterial symbionts – bacterium Sulcia (Bacteroidetes) and a betaproteobacterium – which, in some groups, were lost or replaced by other bacteria. 2. The aim of this research was to: (i) identify the symbiotic microorganisms associated with the invasive treehopper Stictocephala bisonia; (ii) describe their localisation as well as the mode of inheritance; and (iii) address the issue of whether individuals of S. bisonia, living in different areas and feeding on various plants, possess identical, similar or perhaps different symbiotic microbial systems. 3. Individuals of S. bisonia collected in their native range in North America (U.S.A.) and in 11 localities in Europe were investigated using molecular, histological and ultrastructural methods. 4. The results indicate that all the examined specimens are characterised by the same conservative symbiotic system. All of them are host to only two types of bacterial symbiont: Sulcia and the betaproteobacteria belonging to the Nasuia lineage. No other symbionts in any of 36 individuals examined were detected. 5. Both symbionts are localised in a common bacteriome and are transovarially transmitted between generations.