Host and symbiont genetic contributions to fitness in aTrichogramma–Wolbachiasymbiosis

Abstract

The fitness effects associated with Wolbachia infection have wide-ranging ecological and evolutionary consequences for host species. How these effects are modulated by the relative influence of host and Wolbachia genomes has been described as a balancing act of genomic cooperation and conflict. For vertically transmitted symbionts, like cytoplasmic Wolbachia, concordant host–symbiont fitness interests would seem to select for genomic cooperation. However, Wolbachia’s ability to manipulate host reproductive systems and distort offspring sex ratios presents an evolutionary conflict of interest with infected hosts. In the parthenogenesis-inducing (PI) form of Wolbachia found in many haplodiploid insects, Wolbachia fitness is realized through females and is enhanced by their feminization of male embryos and subsequent parthenogenetic reproduction. In contrast, as long as Wolbachia is not fixed in a population and sexual reproduction persists, fitness for the host species is realized through both male and female offspring production. How these cooperating and competing interests interact and the relative influence of host and Wolbachia genomes were investigated in the egg parasitoid Trichogramma kaykai, where Wolbachia infection has remained at a low frequency in the field. A factorial design in which laboratory cultures of Wolbachia-infected T. kaykai were cured and re-infected with alternative Wolbachia strains was used to determine the relative influence of host and Wolbachia genomes on host fitness values. Our results suggest fitness variation is largely a function of host genetic background, except in the case of offspring sex ratio where a significant interaction between host and Wolbachia genomes was found. We also find a significant effect associated with the horizontal transfer of Wolbachia strains, which we discuss in terms of the potential for coadaptation in PI-Wolbachia symbioses.

Wolbachia dominate Spiroplasma in the co‐infected spider mite Tetranychus truncatus

“…Similar results have been obtained in Nasonia vitripennis , when wasps infected with two Wolbachia strains ( w Av and w Bv) appeared to produce more offspring when in different genetic backgrounds to the strains used for comparison, whereas no positive fitness effects were found once host genetic background was controlled (Bordenstein and Werren, ). Fitness variation, including fecundity and survival, will often largely represent a function of host genetic background (Russell et al ., ). The costs we have detected for the Wolbachia and Spiroplasma contrast with the effects of a Wolbachia and Spiroplasma co‐infection in D. melanogaster , where there is no evidence of any benefits or costs when compared with single infections (Montenegro et al ., ).…”

Infection pattern and negative effects of a facultative endosymbiont on its insect host are environment-dependent

“…insecticola were reared on wheat seedlings in Petri dishes as the Regiella -infected strains, and the other thirty aphid clones naturally lacking any known facultative endosymbionts were reared as Regiella -free strains. Previous studies suggested that the effects of endosymbionts on host fitness might be dependent on host and symbiont genotype or an interaction between the two 45,46 . Therefore, the genotype of each aphid clone used in this study was examined using PCR based on six microsatellite loci, S49, Sm10, Sm12, Sav1, Sav2 and Sav4 47,48 .…”

The effect of the endosymbiont Wolbachia on the behavior of insect hosts

“…(ii) It could be due to different Wolbachia/host combinations. Documents have revealed that different Wolbachia strains could induce distinct phenotypes in one host, and one Wolbachia strain may have various effects on different hosts (Dean, 2006;Chafee et al, 2011;Russell et al, 2018). In their case, wVulC Wolbachia is pathogenic and over-replicates reducing the lifespan of its host.…”