Research

Research projects:

 

Paternal genome elimination

In some species of insects and mites the importance of males in reproduction appears to be reduced. In these species, although males are still needed to fertilise females, a female can eliminate his genes from her sons. As a result males, although they receive their fathers genes, will only pass their mothers genes on to their offspring. This peculiar type of reproduction called Paternal genome elimination (PGE) has evolved at least seven times and is found in thousands of species. PGE is thought to have evolved as a result of conflict between genes of the mother and father within their offspring over who gets passed on to the next generation; with PGE considered a victory for the mother's genes. However this theory has never been tested emperically. Therefore the main aim of this project is to test how conflict between the parents genes within their son, has contributed to the origin, maintance and loss of PGE. To do so I am using a number of different study systems, including the citrus mealybug and the human body louse (see below for info on the study systems in our lab).

 

The evolution of Haplodiploidy

Haplodiploidy is a type of reproduction where male develop from unfertilized eggs and have only one copy of each chromosome, while females develop from fertilized eggs and therefore have two copies of each chromosome. Most biologist know about haplodiploidy as it is found in ants, bees and wasps. However haplodiploidy is far more widespread, it is found in about 12% of all species of animals, across insects, mites, nematodes and rotifers. Given its high prevelance it is astounding how little we know about how haplodiploidy evolved and how it affects many evolutionary processes. Our lab is using a combination of theoretical and comparative analyses to improve our understanding of haplodiploidy, especially focussing on mite (Acari) as haplodiploidy has evolved repeatedly in this group.

 

Hermaphroditism in the Icerya scale insects

The scale insects are a group of plant-feeding hemipteran insects that have some of the most bizar reproduction in the animal world. Even among scale insects though one species stands out: the cottony cushion scale insect Icerya purchasi - in which evolution has driven the male to become a parasite living in the body of the female, producing sperm and fertilising her from within. This turns females into functional hermaphrodites. Recent evolutionary theory suggests that this system might have evolved from conflict between males and females over how many eggs a male gets to fertilize (Gardner and Ross 2012). However many questions remain: based on our current understanding we would expect that all reproduction happens through self-fertilization of hermaphrodites. However we do find true males in natural populations, and these males have been shown to mate with the hermaphrodites in the laboratory. This raises the question, can the sperm of these males compete with the sperm already present within the hermaphrodite and can these male infect their daughters with new parasitic male tissue? Other questions include, the role of bacteria living within the cells of Icerya purchasi and why and when mothers produce sons instead of hermaphrodites.

Icerya hermaphrodite with "her" offspring

 

Eusociality

The lab is involved in a number of projects that attempt to understand the link between reproduction, genome architecture, ecology and eusociality. These projects involve a combination of theory as well as large comparative analyses.

Some eusocial species have an equal number of male and female helpers, such as in (A) the thrips Kladothrips intermedius (picture by Holly Caravan) and (B) the termite Macrotermes gilvus (picture by Mitsuhiko Imamori). Other species only have female helpers, such as in (C) the ant Leptomyrmex darlingtoni (picture by Alexander Wild). and (D) the spider Anelosimus eximius (picture by Ken Preston-Mafham).

 

Study systems:

 

The citrus mealybug (Planococcus citri).

On one hand the citrus mealybug is a worldwide pest of agricultural crops, causing millions of damage across the world. On the other hand however, it is the perfect study system for understanding Paternal genome elimination: they are easy to keep in the lab (all you need are some sprouting potatoes!) and we know a lot about their biology.

 

The human body louse (Pediculus humanus corporis)

 

The cottony cushion scale insect (Icerya purchasi)