Wolbachia Age-Sex-Specific Density in Aedes albopictus: A Host Evolutionary Response to Cytoplasmic Incompatibility?

Abstract

Background Wolbachia bacteria have invaded many arthropod species by inducing Cytoplasmic Incompatibility (CI). These symbionts represent fascinating objects of study for evolutionary biologists, but also powerful potential biocontrol agents. Here, we assess the density dynamics of Wolbachia infections in males and females of the mosquito Aedes albopitcus, an important vector of human pathogens, and interpret the results within an evolutionary framework.Methodology/Principal Findings Wolbachia densities were measured in natural populations and in age controlled mosquitoes using quantitative PCR. We show that the density dynamics of the wAlbA Wolbachia strain infecting Aedes albopictus drastically differ between males and females, with a very rapid decay of infection in males only.Conclusions/SignificanceTheory predicts that Wolbachia and its hosts should cooperate to improve the transmission of infection to offspring, because only infected eggs are protected from the effects of CI. However, incompatible matings effectively lower the fertility of infected males, so that selection acting on the host genome should tend to reduce the expression of CI in males, for example, by reducing infection density in males before sexual maturation. The rapid decay of one Wolbachia infection in Aedes albopictus males, but not in females, is consistent with this prediction. We suggest that the commonly observed reduction in CI intensity with male age reflects a similar evolutionary process. Our results also highlight the importance of monitoring infection density dynamics in both males and females to assess the efficiency of Wolbachia-based control strategies.

Population Dynamics and Growth Rates of Endosymbionts During Diaphorina citri (Hemiptera, Liviidae) Ontogeny

“…(Diptera: Glossinidae) and the high densities of the mutualistic symbiont Wigglesworthia [70]. The lowest density of Wolbachia in females of D. citri during the reproductive period as compared to males of D. citri is contrary to previous reports on many other species [13,76,77]. Little is known on the adaptive cost of infection and the presumable differences in the proliferation rate of Wolbachia in the reproductive tissues of males and females [13,76,77], but the lower density of Wolbachia in older females could be a consequence of the reduced growth rate after t* (third instar) and/or due to the process of transovarian transmission.…”

Fitness of wAlbB Wolbachia Infection in Aedes aegypti: Parameter Estimates in an Outcrossed Background and Potential for Population Invasion

“…This may represent an underlying feature of its growth within Ae. aegypti adults as they age; wAlbB densities tend to increase with adult age in both its native hosts 35 and in an experimental infection of Anopheles stephensi. 36 The nonproportional hazard ratio of females infected with wMelPop may reflect its overreplication in host cells, which causes early death as demonstrated in Drosophila.…”

Detection of Low-Level Cardinium and Wolbachia Infections in Culicoides

“…Low-level infections detected only by qPCR and confirmed by nested PCR were found in a range from Ϸ125 to 60,000 target copies per Culicoides insect. Changes in endosymbiont density can be a result of a range of factors, such as the bacterial strain (48,49), host age (49,50), sex (50), and temperature (51,52). Endosymbiont density based on C q values was investigated with Culicoides species that had Cardinium infections in both sexes.…”