Natural interspecific and intraspecific horizontal transfer of parthenogenesis–inducingWolbachiainTrichogrammawasps

Abstract

The intracellular bacterium Wolbachia is one of the most common symbionts in arthropods and, because of its manipulative effects on host reproduction, is assumed to be an important factor in several evolutionary processes. These bacteria are mainly vertically transmitted from mother to daughter through the egg cytoplasm, and horizontal transmission is generally assumed to be rare. Here, we show natural inter-and intraspecific horizontal transfer of parthenogenesis-inducing Wolbachia between parasitoid wasps of the genus Trichogramma. Horizontal transfer was observed when infected and uninfected larvae shared the same host egg. This is the first report, to our knowledge, on interspecific horizontal transfer of Wolbachia between closely related sympatric species. Some originally uninfected immature wasps acquired Wolbachia while inside the host egg, but not all of these newly infected females exhibited the parthenogenesis phenotype. In general, intraspecific horizontal transfer was more successful than interspecific transfer. Wolbachia underwent vertical transmission in the new species but the infection tended to be lost within several generations. Our results have important implications for understanding the evolution of Wolbachia-host associations.

Evolution of early male-killing in horizontally transmitted parasites

“…Moreover, frequent HT from infected to uninfected individuals of another reproductive parasite, a parthenogenesis-inducing Wolbachia, was observed in the parasitoid wasp Trichogramma kaykai [22,23]. Infected and uninfected T. kaykai larvae shared the same host and some of the originally uninfected larvae acquired the infection.…”

Occasional males in parthenogenetic populations of Asobara japonica (Hymenoptera: Braconidae): low Wolbachia titer or incomplete coadaptation?

“…While vertical transmission is the main transmission mode of Wolbachia within established hosts, horizontal transmission plays a major role in the spread of Wolbachia in(to) novel hosts (Hurst et al, 1992;O'Neill et al, 1992;Rousset et al, 1992;Werren et al, 1995;Vavre et al, 1999;Huigens et al, 2000Huigens et al, , 2004Kraaijeveld et al, 2011a). This predicts that upon invasion of a new host population, Wolbachia would initially be selected for efficient horizontal transmission, as well as efficient vertical transmission.…”

“…For example, the parasitoid wasp Leptopilina boulardi is infected with a symbiont that manipulates the superparasitism behavior of its host in order to enhance its own horizontal transmission (Varaldi et al, 2003). Successful experimental horizontal transmission of Wolbachia often leads to unstable infections in the new host and reduced or altered expression of the reproductive manipulation (Grenier et al, 1998;Heath et al, 1999;Huigens et al, 2004;Jaenike, 2007). An explanation for such poor vertical transmission might be residual incompatibilities or asynchronies between Wolbachia and the new host (Heath et al, 1999).…”

Convergent incidences ofWolbachiainfection in fig wasp communities from two continents

“…New infections arise by horizontal transmission from already-infected species (e.g. Heath et al 1999;Huigens et al 2003), and are expected to involve some ecological interaction between the two hosts involved (Werren 1997). In addition, horizontal transmission may be more likely between closely related host species, because they share vectors (e.g.…”