PhD Studentship: Wolbachia Prevalence in UK Lepidoptera: Intimate Friend or Itinerant Foe?

This project is one of a number that are in competition for funding from the NERC Great Western Four+ Doctoral Training Partnership (GW4+ DTP). The NERC GW4+ DTP involves the four research-intensive universities across the South West – Bath, Bristol, Cardiff and Exeter – and six Research Organisation partners. For further details about the programme please see the apply button below.

Studentships will be awarded on the basis of merit and will commence in September 2014. For eligible students the award will cover UK/EU tuition fees and an annual stipend (in 2013/14 this was £13,726 for full-time students, pro rata for part-time students) for three and a half years.

Dr Dave Hodgson, College of Life and Environmental Sciences, University of Exeter
Prof Nina Wedell, College of Life and Environmental Sciences, University of Exeter
Dr Amber Teacher, College of Life and Environmental Sciences, University of Exeter
Dr Jon Bridle, University of Bristol

Project description:  Wolbachia is an endosymbiotic bacteria, supposed to infect > 50% of insect species worldwide. It is inherited matrilineally, and therefore imposes sex-specific selection, including sex-ratio distortion, on its hosts (Charlat et al 2007). This reduces effective and actual population sizes in hosts, with implications for the conservation of insects, including charismatic butterflies and moths. If this host-endosymbiont relationship is intimate and chronic, then coevolutionary processes can select for suppression of harmful effects in hosts. Yet little is known about how host species acquire infection, the process of coevolution, or how many species of Lepidoptera harbour Wolbachia and suffer its impacts.

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Recently we performed the first survey of Wolbachia infection in European moths (344 moths belonging to 117 species across 8 families). Beta-binomial modelling estimated 45% of moth species to be infected with Wolbachia. Sequencing of Wolbachia in 10 species from a single assemblage of moths revealed that a broad taxonomic range of species all shared very similar strains of Wolbachia. This implies strongly that Wolbachia is transmitted horizontally between unrelated species (Boyle et al 1993): prime candidates for the agents of transmission are parasitoid wasps. The primary goal of our proposed project is to examine the diversity and prevalence of Wolbachia infection in 10 geographically distinct moth assemblages around the UK, to determine whether Wolbachia strains are clustered taxonomically (via intimate association with host species), geographically (via itinerant transmission among coexisting species), or both.

In our survey, several moth species showed complete prevalence, while a minority showed intermediate prevalence of infection. The latter are prime candidates to be suffering reproductive manipulations by Wolbachia. Using mating trials, we will test the hypothesis that host species with intermediate prevalence are those that suffer death or feminisation of male embryos, or cytoplasmic incompatibility between infected males and uninfected females. Using artificial infection experiments via micro-injection, we aim to show that “naïve” host species are immediately susceptible to the sex-ratio distortion symptoms of Wolbachia infection.

We expect the project to yield >3 high impact papers, in at least Proceedings of the Royal Society Series B, Evolution, and Functional Ecology. 

Closing date: 10th January 2014

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