Testing evolutionary theory: from genome to phenotype and back again

What do we get from continuing to develop and test evolutionary theory? The picture of evolution we have inherited from the Modern Synthesis is a rich and varied one. We have a good understanding of the genetic inheritance of traits, an appreciation of the role of genetic drift in shaping molecular variation, and have increasingly been able to measure and observe natural selection in the wild. Our recent advances in theory and experiment have added considerable sophistication to our basic view of Darwinian evolution, highlighting the role of genetic constraints on evolution, indirect genetic effects and also conflicts of interest between individuals of the two sexes. But for all the tremendous successes of these developments, it has often been very hard to judge how important each one is in explaining variation in the organisms we see around us. Yet this is what we need to do if we wish to find more general patterns in how organisms adapt and evolve. The main stumbling block has been a lack of traits about which we know a lot about how natural selection should work; only with this information can we begin to ask to what extent is variation from the expected pattern explicable in terms of genetic constraints, sexual conflict and so on. I will use two traits where we do know how natural selection should be acting, sex allocation and female re-mating rate, as model systems to test the importance of aspects of current evolutionary theory. Using the sex ratio decisions of female parasitic wasps, I will explore how genetic architecture and opposing forces of natural selection influence adaptation. Using the mating behaviour of a promiscuous seed bug, I will explore how conflicts of interest between males and females over whether to mate influence other aspects of an organism's biology, such as how long they live, how many offspring they have, and how big they grow. With a mixture of genetic analysis and behavioural experiments in the field and in the laboratory, I will untangle how different evolutionary processes work, and estimate their importance quantitatively. The results will give us valuable insights into how important particular genetic and environmental factors are in limiting the extent to which animals adapt themselves to their surroundings.