Wolbachia Infection in a Natural Parasitoid Wasp Population

Abstract

The maternally transmitted bacterium Wolbachia pipientis is well known for spreading and persisting in insect populations through manipulation of the fitness of its host. Here, we identify three new Wolbachia pipientis strains, wHho, wHho2 and wHho3, infecting Hyposoter horticola, a specialist wasp parasitoid of the Glanville fritillary butterfly. The wHho strain (ST435) infects about 50% of the individuals in the Åland islands in Finland, with a different infection rate in the two mitochondrial (COI) haplotypes of the wasp. The vertical transmission rate of Wolbachia is imperfect, and lower in the haplotype with lower infection rate, suggesting a fitness trade-off. We found no association of the wHho infection with fecundity, longevity or dispersal ability of the parasitoid host. However, preliminary results convey spatial associations between Wolbachia infection, host mitochondrial haplotype and parasitism of H. horticola by its hyperparasitoid, Mesochorus cf. stigmaticus. We discuss the possibility that Wolbachia infection protects H. horticola against hyperparasitism.

Wolbachiaincreases the susceptibility of a parasitoid wasp to hyperparasitism

“…Extremely rarely it also parasitizes Cotesia melitaearum, which is the other specialist endoparasitoid of M. cinxia caterpillars (van Nouhuys and Hanski, 2005). In neighboring Estonia, the butterfly and H. horticola are present but both Wolbachia and the hyperparasitoid are absent (Duplouy et al, 2015;Montovan et al, 2015).…”

“…Because of haplodiploidy, unmated diploid H. horticola is a haplodiploid Hymenoptera, so unmated mothers produce haploid male offspring through arrhenotokous parthenogenesis (Normark, 2003). Wolbachia-infected females transmit the infection to both sons and daughters (Duplouy et al, 2015). The infection status of individual H. horticola females was unknown until after the experiment, but it was assumed that about half the individuals from Åland were infected (Duplouy et al, 2015).…”

“…stigmaticus (Brischke) (Hymenoptera: Ichneumonidae: Mesochorinae). There is a negative correlation between the prevalence of wHho-infected wasps and the prevalence of hyperparasitism in the landscape in Åland (Duplouy et al, 2015). This pattern of association, if causal, could arise in two ways (Fig.…”

“…The wasp occupies the entire host metapopulation (Couchoux et al, 2016). About half of the wasp population is infected by a unique Wolbachia strain, wHho (Duplouy et al, 2015). It is not clear yet how the bacterium is maintained throughout the wasp population.…”

“…It is not clear yet how the bacterium is maintained throughout the wasp population. Duplouy et al (2015) have shown that the transmission rate of the bacterium is high but not perfect. The bacterium has no apparent effect on egg-load, longevity and metabolism of the host wasp, and the sex ratio of the wasp population is not female-skewed.…”