Symbiont interactions with non-native hosts limit the formation of new symbioses

Natalie Niepoth,Jacintha Ellers,Lee M Henry

doi:10.1186/s12862-018-1143-z

Natalie Niepoth, Jacintha Ellers + Show 1 more

Open Access

https://doi.org/10.1186/s12862-018-1143-z

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Abstract

BackgroundFacultative symbionts are common in eukaryotes and can provide their hosts with significant fitness benefits. Despite the advantage of carrying these microbes, they are typically only found in a fraction of the individuals within a population and are often non-randomly distributed among host populations. It is currently unclear why facultative symbionts are only found in certain host individuals and populations. Here we provide evidence for a mechanism to help explain this phenomenon: that when symbionts interact with non-native host genotypes it can limit the horizontal transfer of symbionts to particular host lineages and populations of related hosts.ResultsUsing reciprocal transfections of the facultative symbiont Hamiltonella defensa into different pea aphid clones, we demonstrate that particular symbiont strains can cause high host mortality and inhibit offspring production when injected into aphid clones other than their native host lineage. However, once established, the symbiont’s ability to protect against parasitoids was not influenced by its origin. We then demonstrate that H. defensa is also more likely to establish a symbiotic relationship with aphid clones from a plant-adapted population (biotype) that typically carry H. defensa in nature, compared to clones from a biotype that does not normally carry this symbiont.ConclusionsThese results provide evidence that certain aphid lineages and populations of related hosts are predisposed to establishing a symbiotic relationship with H. defensa. Our results demonstrate that host-symbiont genotype interactions represent a potential barrier to horizontal transmission that can limit the spread of symbionts, and adaptive traits they carry, to certain host lineages.

Highlights

Facultative symbionts are common in eukaryotes and can provide their hosts with significant fitness benefits
Aphid survival and reproduction was influenced symbiont treatment (GLM symbiont treatment: host survival: χ22 = 13.11, p = 0.001; host reproduction χ22 = 66.61, p < 0.001); aphids infected with symbiont strain H218 had lower survival at 7 days after injection and had reduced reproduction when compared to the control injection (Fig. 1)
We found that related pea aphid clones belonging to the major clade associated with the plant L. pedunculatus, which commonly carry H. defensa, were more likely to establish a symbiosis with this symbiont compared to aphids associated with the plant L. corniculatus, which rarely harbor this symbiont in nature

Summary

Introduction

Facultative symbionts are common in eukaryotes and can provide their hosts with significant fitness benefits. Despite the advantage of carrying these microbes, they are typically only found in a fraction of the individuals within a population and are often non-randomly distributed among host populations It is currently unclear why facultative symbionts are only found in certain host individuals and populations. Host specificity is common in endosymbiotic partnerships and is found in many host-symbiont associations, Some of the best examples of facultative symbionts providing hosts with advantageous traits are found in the endosymbiotic bacteria of insects. These microbes can confer an array of benefits that have the potential to increase their host’s fitness in certain ecological conditions [12]. Facultative symbionts can benefit insects by protecting them from natural enemies, buffering against heat stress, aiding in plant-feeding, providing nutrients, and even detoxifying pesticides

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