Host genotype–endosymbiont associations and their relationship with aphid parasitism at the field level

Abstract

1. The relationship between endosymbionts and insects represent complex eco‐evolutionary interactions. Vertically transmitted endosymbionts can be a source of evolutionary novelty by conferring ecologically important traits to their insect hosts, such as protection against natural enemies. Host–endosymbiont associations could constitute an adaptive complex (holobiont) on which selective pressures present in the environment can act, being transferred to the next generation.2. Although several laboratory‐based studies have confirmed host genotype × symbiont interactions, few studies have been directed at those associations in the natural populations and their ability to protect themselves from parasitism pressure at the field level.3. A field‐based approach to study the aphid genotype–endosymbiont associations and its relationship with the total parasitism in the grain aphid Sitobion avenae was conducted. From the field study, experiments were carried out to study the defensive effect of the two most common facultative endosymbionts (Regiella insecticola and Hamiltonella defensa) present in S. avenae against one of the most important parasitoid species, Aphidius ervi.4. Evidence is presented here of a high specificity of the aphid clone–endosymbiont associations in the field; however, the field and experimental results here do not support a relationship between the aphid clone–endosymbiont associations and a proxy of total parasitism in S. avenae. These findings highlight the importance of particular host clone–endosymbiont couplings as a key factor in gaining an understanding of the coevolutionary dynamics of endosymbionts in nature and their effect on the invasive potential of pest insects.

Low bacterial community diversity in two introduced aphid pests revealed with 16S rRNA amplicon sequencing

“…However, the read abundance should be interpreted carefully when it is used as an estimate of the infection frequency of endosymbionts, because PCR amplification bias can be introduced by primer specificity ( Klindworth et al, 2012 ). Despite this, our results from the deep sequencing of 16S rRNA gene are consistent with previous PCR-based studies on Chilean populations of S. avenae , in which ∼50% of the aphids harbored R. insecticola and a lower proportion of aphids harbored H. defensa (between 4% and 15%) ( Sepúlveda et al, 2016 ; Zepeda-Paulo, Villegas & Lavandero, 2017 ), suggesting that the aphid-endosymbiont associations can vary across geographic range of aphid species.…”

“…Specifically, aphid secondary endosymbionts can protect the host from natural enemies, can provide tolerance to heat shock and can facilitate the colonization of new host plants ( Oliver et al, 2010 ). Although recent studies have not found evidence that the endosymbionts R. insecticola nor H. defensa can confer defense against parasitoid wasps in S. avenae ( Łukasik et al, 2013 ; Zepeda-Paulo, Villegas & Lavandero, 2017 ), at least one strain of R. insecticola has shown to provide protection to S. avenae against the pathogenic fungus Pandora neoaphidis ( Łukasik et al, 2015 ). This symbiont-mediated advantage could explain the higher prevalence of R. insecticola in the populations of S. avenae here studied; however, this is not consistent with the lower prevalence of this endosymbiont reported in native regions of S. avenae.…”

Detection and geographic distribution of seven facultative endosymbionts in two Rhopalosiphum aphid species

“…() that different host species could exhibit different symbiont combinations. Furthermore, significant difference of infection frequencies can be found even from different genotypes of the same aphid species (Zepeda‐Paulo, Villegas, & Lavandero, ). A higher proportion of European R. padi harbored three, four and five symbionts simultaneously compared with Chinese samples indicating that the infection frequency of facultative symbionts may differ significantly between distant geographical regions.…”

Facultative bacterial endosymbionts shape parasitoid food webs in natural host populations: A correlative analysis

“…For example, some pea aphid genotypes have been shown to resist A. ervi in the absence of endosymbionts, although the symbiont‐encoded resistance has still been suggested to be the most important mechanism for aphid–parasitoid defence (Martinez, Ritter, Doremus, Russell, & Oliver, ). In S. avenae , specific host genotype–endosymbiont associations have been found, however, parasitism rate was unaffected by these host genotype–endosymbiont associations (Zepeda‐Paulo, Villegas, & Lavandero, ). Bearing this in mind, our results seem not to be affected by endosymbiont–host genotype associations and they indicate that H. defensa and R. insecticola primarily affect immature parasitoids by killing them within their aphid hosts rather than by avoiding the parasitoids’ oviposition into infected aphids.…”