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How common are heritable microbes, and why?

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  • Full or part time
    Dr SJ Cornell
    Prof G Hurst
  • Application Deadline
    No more applications being accepted
  • Competition Funded PhD Project (European/UK Students Only)
    Competition Funded PhD Project (European/UK Students Only)

Project Description

Heritable endosymbionts are extremely common, being observed in around 30% of all arthropod species. Their pervasiveness is very puzzling from an evolutionary perspective, because any host species represents a dead end to a symbiont that is only transmitted vertically (i.e. from parent to offspring). There must be some degree of horizontal transmission, but this has hardly ever been observed. Moreover, the true incidence of endosymbionts is very poorly known because detection methods are unreliable. It is therefore extremely challenging to understand how new host-symbiont interactions arise and are maintained across evolutionary lineages.

This PhD project will address this problem by constructing theoretical models that relate observed patterns of symbiont incidence to transmission processes between species. These models need to account for: the evolution of virulence, and hence transmissibility, within hosts; the relationship between transmission rates and genetic relatedness; and the role played by currently extinct species that may have acted as historical intermediates for infection. Bayesian statistical methods can exploit mechanistic knowledge of the PCR methods used for symbiont detection to better infer true prevalence from apparent incidence. The processes responsible for cross-species transmission and host-symbiont evolution will be inferred by fitting to phylogenies in different taxonomic groups. The predicted relationship between genetic distance and symbiont compatibility will be confirmed by experimental infections in Drosophila.

This project would suit a graduate of a quantitative discipline (e.g. mathematics, physics, computer science) who wishes to apply their skills to evolutionary biology, or a biologist with strong mathematical and/or computational skills. The project will be supervised by Dr. Stephen Cornell (theoretical ecologist) and Prof. Greg Hurst (evolutionary biologist).

Funding Notes

Competitive funding of tuition fee, research costs and stipend (£14,777 tax-free, 2018-19) from the NERC Doctoral Training Partnership ACCE, View Website. ACCE – a collaboration between the Universities of Sheffield, Liverpool, and York – is the only dedicated ecology/evolution/conservation Doctoral Training Partnership in the UK.

Applications (CV, letter of application, 2 referees) by email to [Email Address Removed], deadline: January 9 2019. Interviews in or after the week commencing: 11th February 2019. Shortlisted applicants will be interviewed for only one project from the ACCE partnership.

This project is also available to self-funded students. A fees bursary may be available.


N Gerardo, G Hurst 2017 Q&A: Friends (but sometimes foes) within: the complex evolutionary ecology of symbioses between host and microbes BMC biology 15, 126.

E Chrostek, K Pelz-Stelinski, GDD Hurst, GL Hughes 2017 Horizontal transmission of intracellular insect symbionts via plants Frontiers in microbiology 8, 2237.

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