Sex Determination and the Extinction Vortex

About the Project

This PhD will investigate whether the risk of extinction in Hymenoptera is greater than most other insect species because of a synergistic interaction between extrinsically driven decline and an intrinsic factor, their mechanism of sex determination.

Insects are essential to ecosystem function but are declining because of extrinsic, human-derived impacts on environments [1]. Ants, bees and wasps - the most ecologically important insect Order (Hymenoptera) - provide services such as pollination, seed dispersal and soil turnover that are fundamental to almost all terrestrial environments and play an essential role in global food production.

Most studied Hymenoptera have complimentary sex-determination (CSD) [2]. The functioning of CSD requires genetic variation at the CSD locus. Low genetic variation, caused by small population size / habitat fragmentation, leads to diploids that usually develop into females developing into diploid males (DM). Modelling shows that DM production greatly increases the likelihood of extinction [3]. However, the dynamics of CSD genetic variation in natural populations has only been studied in honey bees because knowledge of the genetic underpinning of CSD was restricted to this species group [4,5]. Recent research suggests the molecular mechanism is conserved in ants [6,7]. This enables, for the first time, 1) empirical studies of CSD genetic variation in natural populations and tests of the synergistic effect of CSD and population decline, 2) the potential to develop rapid molecular genetic assays that could highlight perilously low CSD genetic variation and aid decisions to intervene by genetic rescue [8].

This PhD will focus on ant species with populations that have within their range both contiguous/large and fragmented/small populations (e.g., northern/central European populations in contiguous habitats vs southern range, altitudinally limited populations).

Objective 1: Confirm the molecular basis of CSD in the selected species.

Objective 2: Survey genomic variation using whole genome re-sequencing in replicated populations of contiguous/large and fragmented/small population types.

Objective 3: Compare genetic variation at CSD with: 1) other regions of the genome, 2) across the two population types. Test whether balancing selection acting on CSD maintains / does not maintain variation in small/fragmented populations.

Objective 4: Investigate developing a CSD rapid genotyping assay using Nanopore long-read sequencing that works in multiple species.

Training opportunities: This project integrates fieldwork (ant collection in UK and continental Europe), DNA sequencing using Illumina and Nanopore platforms, molecular techniques such as DNA extraction, PCR, genetic library construction and advanced bioinformatic analysis (UNIX, R and specialised programmes) using the University of Leicester’s powerful HPC cluster ‘ALICE’. You will learn to analyse large genomic datasets, apply modern statistics in the R programming framework, and effectively communicate your results to academic, conservation stakeholder and public audiences.

Outputs: Your work will lead to at least two high-quality papers in international peer-reviewed journals. You will attend and present your work (talks/posters) at international conferences on population/evolutionary genetics and conservation biology. You will also promote your work to the public through press releases, articles for a lay audience and presentations to the public and conservation stakeholders.