Influence of Continuous High Temperature Conditions on Wolbachia Infection Frequency and the Fitness of Liposcelis tricolor (Psocoptera: Liposcelididae)

Endosymbiotic bacteria that potentially influence reproduction and other fitness-related traits of their hosts are widespread in arthropods, and their appeal to researchers' interest is growing. In this study, the influence of continuous high temperature conditions on Wolbachia infection frequency and the fitness of Liposcelis tricolor (Psocoptera: Liposcelididae) was studied in a laboratory. The results showed that the Wolbachia infection frequency was gradually decreased when L. tricolor was reared at 33 degrees C; after six generations of treatment, no Wolbachia wsp gene product was detected, suggesting that the Wolbachia infection was completely eliminated. The combined immature development periods and survival rates of L. tricolor did not vary significantly among six generations; however, the female longevities and fecundities dramatically declined from F-1 through F-6, resulting in decreasing values of population intrinsic rate of increase (r(m)). Using r(m) values, the fitness for F-2, F-3, F-4, F-5, and F-6 relative to F-1 was calculated as 0.995, 0.953, 0.811, 0.700, and 0.552, respectively. We realize that it is not possible to distinguish between the effects of high temperature may have on the metabolic processes of the psocids and the effects of temperature-induced reduction in bacterial infection frequencies. Our study confirms that the combined use of antibiotics and heat treatment is a good control measure for psocids.