The evolution of hermaphroditism in insects

Summary
Organisms reproduce in diverse ways. Yet it is unclear why and how new reproductive strategies evolve. This project focuses on the only case of hermaphroditism in insects: In species of the scale insect Icerya female-like hermaphrodites produce both sperm and eggs and self-fertilize.

Project background
Understanding why there is such variability in the way organisms reproduce is one the most important unsolved puzzles in evolutionary biology. This project aims to tackle this question by focusing on the unique and puzzling reproductive strategy of the scale insect Icerya purchasi. This species is the only insect unequivocally described as hermaphroditic; female-like hermaphrodites can produce both sperm and eggs and self-fertilize. But how can a female produce sperm? A recent hypothesis suggests that the sperm present in hermaphrodites seem to have originated from the individuals father “infecting” his future offspring with sperm-producing cells. However although the data is suggestive, this hypothesis requires further scrutiny. It is also unclear why, while most offspring develop as hermaphrodites, a small number develop as males. Finally it seems that while hermaphroditism is exceedingly rare in insects, it might have evolved independently in several close relatives of Icerya. This PhD project will explore how and why this unusual reproductive system evolved by using comparative methods across species as well as experimental and genomic analyses in the laboratory. Together this work will help us to better understand what evolutionary forces shape the ways animals reproduce.

Research questions
The projects sets out to test a number of key questions to better understand the evolution of the only insect hermaphrodite:

What is the evolutionary and developmental origin of the sperm produced by female-like hermaphrodites?
Hermaphrodites can self-fertilize, so why and how do they occasionally produce male offspring?
How frequently did hermaphroditism evolved within the clade of insects and do any ecological factors predict the patterns we observe?

Methodology
The project will use two main approaches:

The first will focus on collecting insect specimens of different Icerya species, and then use molecular phylogenetic methods to determine their evolutionary relationships, and to study transitions between reproductive strategies employed by the different species. This part of the project is in collaboration with Prof. Penny Gullan, The Australian National University, Canberra. (year 1)

The second part of the project will focus on Icerya purchasi. This will use laboratory experiments and a combination of state-of-the-art cytogenetic and genomic approaches to study different aspects of the reproduction of this species. (year 2&3)

Training
A comprehensive training programme will be provided comprising both specialist scientific training and generic transferable and professional skills. Specifically the student will undertake training in the use of molecular wet lab techniques, the analysis of sequencing data and the use of microscopy and cytogenetic approaches.

Requirements
Candidates must be highly motivated with a keen interest in evolutionary biology and genetics and a strong motivation to pursue a scientific career. Previous experience working with insects and phylogenetic and genomic analyses would be an advantage.