Seasonal changes in the density of the symbionts Buchnera and Wolbachia of the aphid Tuberculatus macrotuberculatus on Quercus dentata

Abstract

Seasonal changes in leaf traits and tannins, including hydrolysable tannins (HTs) and condensed tannins (CTs), affect aphid body size and demographic patterns. The aphid Tuberculatus macrotuberculatus Essig & Kuwana (Hemiptera: Aphididae) feeds on the leaves of the daimyo oak, Quercus dentata Thunberg (Fagaceae), does not alternate hosts, and is attended continuously by ants. Buchnera aphidicola Munson et al. (a γ‐proteobacterium, hereafter Buchnera) is the primary symbiont of most aphid species. It provides essential amino acids to host aphids. Wolbachia sp. (an α‐proteobacterium) is present in some aphid species. This study investigated the effects of seasonal tannin and leaf trait fluctuations in Q. dentata on aphid performance and Buchnera and Wolbachia densities in T. macrotuberculatus. As the season progressed, the water content and HT concentration in Q. dentata leaves decreased, CT concentration in Q. dentata leaves increased, and T. macrotuberculatus performance decreased. Buchnera density varied in accordance with host aphid performance, whereas Wolbachia density did not vary throughout the season, suggesting that although Buchnera depends on the host plant and host aphid performance for growth, Wolbachia may have a high tolerance for oligotrophic environments and may exist independent of the nutritional metabolism of the host aphid. Although the role of Wolbachia in T. macrotuberculatus remains unclear, it may be associated with resistance to parasitoid wasps and plant secondary metabolites.