D3460: Hawaiian seed bugs and their microbes: A story of evolution and adaptation

Seed-feeding Nysius insects (Hemiptera: Lygaeidae) have a symbiotic association with distinct intracellular bacteria, “Candidatus Schneideria nysicola” (Gammaproteobacteria). While many other hemipteran insect groups generally rely on bacterial symbionts that synthesize all ten essential amino acids lacking in their plant sap diets, the nutritional role of Schneideria in Nysius hosts that specialize on a more nutritionally complete seed-based diet has remained unknown. To determine the nutritional and functional capabilities of Schneideria, we sequenced the complete Schneideria genomes from three distantly related endemic Hawaiian Nysius seed bug species. The predicted nutritional contribution of Schneideria includes four B-vitamins and five of the ten essential amino acids that likely match its hosts’ seed-based diet. Disrupted and degraded genes in Schneideria suggests that Hawaiian lineages are undergoing continued gene losses observed in the smaller genomes of other more ancient hemipteran symbionts. Furthermore, our analysis of Schneideria in seed-feeding Hawaiian Nysius has set the stage for our current investigation into the role of microbial symbionts in the evolution and remarkable adaptations of the only two carnivorous scavenger species among Hawaiian Nysius seed bugs: the wēkiu bug and the a‘a bug.