Evolutionary genetics of sexual dimorphism

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Understanding the forces that shape the, often spectacular, sexual differences in behaviour, morphology, and physiology is one of the central puzzles of evolutionary biology. In some systems, we know much about the forces of selection shaping these traits, while in other systems we know much about their genetics. My proposal will focus on connecting these currently disparate programs with three more specific themes. In the first, we will bring the new tools of developmental genetics and genomics to a group for which we know much about sex specific selection. These tools, combined with our expertise in behaviour and trait function in the group will allow us to do truly integrative research, linking selection to function, development, expression and genome evolution. We will focus on the genus Rheumatobates, where we have identified a major transcription factor involved in building dimorphic antennal traits in one species. We will undertake a comparative study of antagonistic trait function in the genus Rheumatobates, and conduct knockdowns to determine if similar genetic factors underlie these diverse traits. Expression analyses in wild vs knockdowns will allow us to identify the downstream genes involved in creating the differences in these traits observed among species. In the second theme, we will begin a new program studying the remarkable sexual dimorphism of the large and economically important long-horned beetle group. Here, we will develop a hypothesis for the relationships among species in a large tribe of these beetles, and study the history of the evolution of dimorphism in the group. Subsequently, we will measure the forces of selection that may account for the variation in dimorphism that we see. Finally, we will initiate a study of the genetic model species Caenorhabditis elegans, which provides an underappreciated opportunity to link existing knowledge about gene function and genomics to currently understudied sex specific selection. Using 40 sequenced wild isolates we aim to look for signs of evolutionary divergence in male function and its coevolution with hermaphrodites. The next step will be to find some of the genetic factors that drive this variation and study their evolution. Taking advantage of the available tools we also plan to employ CRISPR/Cas9 genome editing to insert a synthetic and sexually antagonistic locus into an evolving population, with two alleles: a male-detrimental allele and a female-detrimental allele. After experimentally evolving these populations for 40 generations, we will quantify changes in allele frequency and population fitness. We hypothesize that antagonism will be masked in some populations through independent suppressor mutations, while others may maintain antagonism and even accumulate additional antagonistic alleles. This project will be the first empirical study to follow a sexually antagonistic locus in forward time.