Endosymbionts as an overlooked threat for insect reintroductions

Description

Species reintroduction - or augmentation - into restored habitat will be increasingly used to combat biodiversity loss in a rapidly changing world, and used for a wider range of taxa, including invertebrates. Key tenets of this biodiversity restoration approach are to use source populations that are ecologically compatible with the target site, and to maximise genetic diversity. However, it is unusual to consider potential incompatibilities between different lineages arising from the effects of endosymbionts, which are common and may significantly impact conservation objectives.

In 2018, Butterfly Conservation began a reintroduction programme of the Chequered Skipper butterfly (Carterocephalus palaemon), which went extinct from England in 1976, using source populations from Belgium. Recent genetic studies have shown an unexpected degree of divergence between the source populations, and that only one of the reintroduced genetic lineages has persisted in England. There is strong circumstantial evidence that the elimination of one founder lineage was caused by the presence of incompatible Wolbachia strains. The bacterial endosymbiont Wolbachia is common across insects, and uses cytoplasmic incompatibility and male killing to promote its own transmission. In our study population it is ubiquitous, and shows two diverged strains that correspond with the mitochondrial phylogeny. Better understanding of the endosymbiont interaction is critical to the establishment of a functioning metapopulation of Chequered Skipper across the reintroduction landscape, and more generally to developing best practice protocols for reintroduction biology.

In this PhD project, we aim to establish the operation of cytoplasmic incompatibility in the Chequered Skipper, and to predict its consequences. Our main objectives are to:

1.      Establish direct evidence for cytoplasmic incompatibility in C. palaemon using crossing experiments

2.      Explore the mechanism of cytoplasmic incompatibility with respect to candidate genes in Wolbachia and coevolutionary selection in C. palaemon

3.      Reconstruct the evolutionary origins and spread of the incompatible Wolbachia strains, using a phylogeographic approach

4.      Track the survival of C. palaemon/Wolbachia lineages in reintroduced English populations.

The project is a collaboration between researchers at the University of Liverpool, Butterfly Conservation, and Research Institute for Nature and Forest (Belgium).

Novelty

Wolbachia infection is very common in insects but essentially ignored by conservation practitioners as a potential risk factor. We have uncovered a likely case of bidirectional cytoplasmic incompatibility, which is poorly understood in general and studied in a small number of model systems.

Timeliness

The reintroduction of Chequered Skipper to southern England is ongoing, at significant cost associated with habitat management and translocations, with the longer-term objective of establishing a self-sustaining metapopulation across a small network of habitat patches. So far, a maximisation of genetic diversity strategy has been adopted and there is a real concern that mutually incompatible sub-populations will establish in different habitat patches, preventing effective metapopulation dynamics. Better understanding of the host-parasite interaction will have immediate practical benefits for how the reintroduction is managed.

Essential and Desirable Criteria

Essential

Degree in relevant study area

Interest and intermediate level background in evolutionary genetics and ecology

Experience/aptitude in rearing insects

Bioinformatics experience/aptitude

Desirable

M-level qualification in relevant study area

Experience of analysing genomic data

Phylogenetic analysis

Statistics (R)

Molecular biology

Fieldwork experience/aptitude

Natural history/identification

Experience with Geographic Information System

Competence in written and oral communication (in English)

How to Apply

Notes and details of how to apply are available here: https://accedtp.ac.uk/phd-opportunities/

Informal enquiries to Ilik Saccheri () are welcome.

All applicants to ACCE must complete the ACCE personal statement proforma. This is instead of a personal/supporting statement or cover letter. The proforma is designed to standardise this part of the application to minimise the difference between those who are given support and those who are not. Candidates should also submit a CV and the contact details of 2 referees.

Part-Time Study Options

All ACCE PhDs are available as part time or full time, with part time being a minimum of 50% of full time. Please discuss potential part time arrangements with the primary supervisor before applying to the programme.

Co-funding notes

This project benefits from a monetary contribution and in-kind support from the co-funding partner, Butterfly Conservation. In-kind support, in the form of assistance with fieldwork and rearing experiments will also be provided by the Belgian partner. Importantly, the student will benefit from ongoing work by the supervisors on the genomics and ecology of adaptation to environmental change in Lepidoptera. 

Availability

Open to students worldwide

Funding information

Funded studentship

NERC ACCE DTP programme starts from October 2024.
UKRI provide the following funding for 3.5 years:
• Stipend (2023/24 UKRI rate £18,622)
• Tuition Fees at UK fee rate (2023/24 rate £4,712)
• Research support and training grant (RTSG)
Note - UKRI funding only covers UK (Home) fees. The DTP partners have various schemes which allow international students to join the DTP but only be required to pay home fees. Home fees are already covered in the UKRI funding, meaning that successful international candidates do not need to find any additional funding for fees.

Supervisors

References

Halford G, Maes D, Yung CJ, Whiteford S, Bourn NAD, Bulman CR, Goffart P, Hodgson JA, Saccheri IJ (2024) Genomic monitoring of a reintroduced butterfly uncovers contrasting founder lineage survival. Evolutionary Applications (in review).
Lohse K, Ebdon S, Mackintosh A, Martin S, Saccheri IJ, Bourn NAD, Vila R, et al. (2023) The genome sequence of the Arctic Skipper, Carterocephalus palaemon (Pallas, 1771). Wellcome Open Research 8:369 (https://doi.org/10.12688/wellcomeopenres.19573.1).
Halford, G., Bulman, C. R., Bourn, N., Maes, D., Harpke, A., & Hodgson, J. A. (2024). Can species distribution models using remotely sensed variables inform reintroductions? Trialling methods with Carterocephalus palaemon the Chequered Skipper Butterfly. Journal of Insect Conservation. (https://doi:10.1007/s10841-024-00555-6).
Maes D, Ellis S, Goffart P, et al. (2019) The potential of species distribution modelling for reintroduction projects: the case study of the Chequered Skipper in England. Journal of Insect Conservation 23: 419–431 (https://doi.org/10.1007/s10841-019-00154-w).