The Evolutionary Dynamics of Genetic Conflict: the Origin, Maintenance and Loss of Paternal Genome Elimination.

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Reproduction across the tree of life: Why so many ways of doing it?During sexual reproduction, two unrelated individuals cooperate to achieve a common goal: pass on their genes to the next generation. This cooperation is however not without conflict, parents can fight over who raises the kids, and partners can cheat and mate with other mates. Despite these conflicts genes of the mother and father are, at least in most animals, equally represented in the offspring. This is, however, not always the case. In my research I study a group of insects whose reproduction is incredibly variable and where evolutionary innovations appear to have reduced the importance of males. For example in the citrus mealybug (a plant parasite) and the human body lice (our own parasite), males are still needed to fertilize females, but the female can eliminate his genes from her son. This unusual type of reproduction called "Paternal Genome Elimination" (PGE) is in the female's interest as her sons will always pass on her genes, instead of those of her partner. I use these two species to study how conflict between the sexes can have lead to the evolution of this strange reproductive behaviour. I aim to understand how males and females compete by studying the behavior of their genes within their offspring, using a range of state-of-the-art genetic techniques. In mealybugs we know that a father's genes are not simply eliminated from its sons sperm, but also prevented from being expressed. I aim to study the expression of paternal genes in males of both mealybugs and lice to understand if these genes might have the opportunity to fight against their elimination.The way a father's genes are eliminated from his sons is still unclear, although it seems to take place in the testis while sperm is produced. I aim to study the mechanism of elimination in lice by comparing the process of sperm production in males with and without PGE. Some of the finest minds in evolutionary biology have theorized about the evolution of PGE, yet to date, none of these theories have been tested empirically. Here I will use the human body louse, in which PGE has only recently been discovered to test these theories. I will use crosses between individuals with and without PGE to study how this trait is inherited and how it can spread though the population.In most species with PGE it seems that the mother's genes have won and ensured that they are the ones their sons will pass on to his children. This might not always be the case though. In the final project of this proposal I will study a clade of Australian insect, closely related to mealybugs. Previous research suggests that some species have lost PGE and might have reverted back to "normal" reproduction. I will study species across this clade to see how often PGE has been lost and which factors might be responsible.Taken together, these approaches will address the forces responsible for the evolution of an unusual reproductive system. This knowledge will help scientists understand why reproduction, a process so fundamental, is so variable across life.