PhD studentship! Deadline Jan 8th 2026

Cryptic fitness consequences of a selfish X chromosome

NERC application link:
https://www.exeter.ac.uk/study/funding/award/?id=5761​
For inquiries, please email: [email protected]

Based in:
University of Exeter, Penryn, Cornwall, UK.

Supervisory team:
Mark A. Hanson (University of Exeter, Penryn), primary
Bram Kuijper (University of Exeter, Penryn)
Helen White-Cooper (Cardiff University)

Project description:

​Selfish X chromosomes are a fascinating form of ‘unfair’ mendelian genetics. Males bearing a selfish X can sire only female offspring as Y-bearing sperm are destroyed during spermatogenesis by the selfish X, suggested to be through the action of toxin/antitoxin-like systems. This biology is found in flies and rodents, and likely exists in other taxa that are less easily studied. Population genetics research has focused primarily on selfish X fecundity effects, alongside roles for selfish chromosomes in driving speciation. However, these chromosomes commonly bear multiple inversions to suppress recombination, maintaining genetic linkage of toxin/antitoxin-like systems. As a result, these chromosomes accumulate deleterious mutations that are unaccounted for in existing gene drive models. The student will investigate various stress parameters to reveal cryptic consequences of the selfish chromosome of Drosophila testacea, chosen for its newly-described genetic tools allowing individuals to be genotyped by eye. Key findings will be tested in additional species. The student will influence developing research directions based on initial screens. The student will learn gene-editing, molecular biology, microbiology, and population genetics modelling. The supervisory team includes experts in infection and stress responses, reproductive biology, and population genetics, providing the student the opportunity to develop expertise in key disciplines.

This project fits the NERC 'population ecology and population genetics and evolution remit. Left unchecked, selfish chromosomes can drive species to extinction. As a result, suppressors of selfish X meiotic drive evolve, resulting in coevolutionary arms races that can drive sterility and speciation between populations that evolve along different trajectories.

I (Mark) am personally quite excited to return to this system, which I helped to discover over a decade ago (Keais, Hanson et al., 2017). The recent advances made by Steve Perlman's lab have opened the door to high-throughput experimentation with the selfish X, the first system of its kind to permit stable maintenance of wild-type and selfish X visible genetic markers without repeated crossing schemes. The seemingly full suppression of recombination across the X makes this particular selfish chromosome an ideal model for testing how Müller's ratchet impacts the fitness of this selfish supergene. The lab is additionally actively pursuing funding via multiple routes to do additional work related to the selfish X with the aim of producing functional genetics tools in this system. The lab has a full intent to create a vibrant and exciting research space pushing the forefront of selfish X evolutionary and functional genetics.