Disparities in species divergence: the genomics of large vs small genera

Project overview

Across all walks of life, from bacteria to plants and animals, there are examples of ‘mega-diverse’ genera, often sitting in groups containing other much smaller genera.

What are the evolutionary causes and constraints behind this disparity in species numbers? This project investigates some key hypotheses.  

Project description

The origin of new species represents a fundamental evolutionary process, with one lineage becoming two. In some species, the genomics of speciation have been investigated and key genes and processes implicated. However, we lack information on why the speciation rate differs between lineages. 

In some groups, speciation is rapid, with many species originating in short periods of time, whereas in others this is slow.

There are several examples where members of the same family differ in their number of species by more than 10-fold (for example in the Amaryllidaceae, Caryophyllaceae and Cyperaceae). Why are some lineages apparently prone to speciation and others not? The goal of this project is to investigate this from genomic and ecological angles. 

We break this down into the following stages. We focus on the British flora as it is one of the best studied in the world: 

• UK flora-wide, identify closely related genera which differ in number of species by more than 10-fold. 
• Produce phylogenies to examine speciation rate and date the events, examining whether climate change and glaciation could have played a role. 
• Working with herbarium samples and greenhouse-grown plants, examine changes in life history (e.g., annual or perennial), genome size, ploidy, and other phenotypes to determine whether rapid speciation is linked to these traits. 
• Examine mutation rate, both across species, and from a mutation accumulation experiment to determine whether faster speciation is linked to faster mutation rate. 

The student will learn wet lab skills, bioinformatics and experience working with herbarium material. 

Training

Our programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered and hosted at the University of Southampton.

Specific training will include:  

• Data analysis in R.
• Bioinformatics and command line computing.
• DNA/RNA extraction and sequencing.
• Working with modern and herbarium samples, including ancient DNA sampling and analysis.   

Entry requirements

A UK bachelor’s degree with upper second-class honours or higher in a relevant subject. See international equivalent qualifications on our website.

English language: IELTS 6.5 overall, with a minimum of 6.0 in all components. We accept other English language tests.

Further reading

Moonlight et al. (2024) Twenty years of big plant genera. https://doi.org/10.1098/rspb.2024.0702

Jackson et al. (2024) Genomics of ecological adaptation in Canary Island Descurainia (Brassicaceae) and comparisons with other Brassicaceae. https://doi.org/10.1002/ece3.70144

Strand and Panova (2015). Size of genera – biology or taxonomy? https://doi.org/10.1111/zsc.12087