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Uncovering the Drivers of Diversification in an Exceptional Plant Genus (Petalidium) in the Namib Desert of Southern Africa

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  • Full or part time
    Dr Kyle Dexter
  • Application Deadline
    No more applications being accepted
  • Competition Funded PhD Project (Students Worldwide)
    Competition Funded PhD Project (Students Worldwide)

Project Description

Tropical rain forests and Mediterranean-climate regions host the highest plant diversities in the world, while deserts, whether hot or cold, often have few species. There are exceptions, and the aim of this project is to understand one astounding exception, the genus Petalidium (Acanthaceae) in the Namib Desert. The Namib Desert is one of the driest regions on earth, yet the genus Petalidium has acquired remarkably high species richness in this region (39 species). Even more exceptionally, it has achieved this diversity in the last 500,000 years, and thus represents one of the fastest radiating plant genera in the world. The genus also achieves exceptionally high abundance in this arid environment. At present, it is unknown what has allowed this genus to be so ecologically and evolutionarily successful in the Namib Desert. This project will determine the relative importance of geographic isolation, pollinator switching and environmental niche divergence in driving speciation in Petalidium and may also assess the functional traits that underlie its dominance.

Many species of Petalidium have narrow geographic ranges, some even being restricted to a single mountain ridge; meanwhile, species are not usually found in sympatry, though there are interesting exceptions to this pattern. Long-distance dispersal and subsequent isolation of populations may be the main driver of speciation in this genus, as it is in many biological systems. However, species of Petalidium also show remarkable variation in floral form, from large, tubular red flowers that are indicative of bird pollination to open purple flowers indicative of bee pollination. Divergence in floral form often reflects selection by different pollinators and can lead to reproductive isolation, suggesting the potential for pollinator-switching to drive speciation in the genus.

The lead supervisor Dexter and co-supervisor Tripp have conducted multiple expeditions to Namibia and South Africa, and they have extensive experience with the logistics, ecology and botany of the area. They have already published papers describing several Acanthaceae species that are new to science from Namibia and more are expected in Petalidium. More generally, lead supervisor Dexter is an expert on the evolutionary ecology of tropical plants. Co-supervisor Tripp is one of the foremost young plant systematists in the U.S.A.

Key Research Questions:
1) Does divergence in floral morphology (the shape and colour of flowers) lead to reproductive isolation via visitation by different pollinators?
2) What is the rate of gene flow, if any, among isolated populations of Petalidium and among different species?
3) What functional traits underlie the ability of Petalidium to survive and prosper in such a harsh environment?

Methodology and Training:
A comprehensive training programme will be provided comprising both specialist scientific training and generic transferable and professional skills. The student will acquire skills in 1) field methods in botany and plant reproductive biology, 2) molecular laboratory methods, 3) data analysis in the R statistical environment, 4) scientific writing for both grant applications and journal articles, 5) scientific presentation skills, and 6) inter-institutional and inter-cultural collaboration and networking.

The student will gain experience in tropical field botany and working with collaborators from different countries during at least one field expedition to southern Africa. During the expedition(s), reproductive biology characteristics will be measured in the field while herbarium vouchers, DNA samples, and flower tissue specimens will be collected for later analysis in herbaria and molecular laboratories. The student will also gain valuable collaboration skills during a visit to Tripp’s institution in the U.S.A. (University of Colorado). The student will be trained in scientific presentation in order to give presentations at national and international conferences. Finally, the student will be encouraged to and helped in applying for external grant funding and in publishing his or her work in scholarly journal articles.

Funding Notes

To be eligible to apply for a fully-funded DTP studentship, you must:

1. be a UK or EU citizen or a non-EU citizen with permanent settled status in the UK (known as ‘indefinite leave to remain’)
2. have been ordinarily resident in the UK for at least 3 years prior to the start of the studentship (this applies to all citizen categories).

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FTE Category A staff submitted: 104.98

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