Uncovering gene regulatory networks responsible for the morphological differences between Drosophila simulans and Drosophila mauritiana male genitalia

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External male genitalia structures have frequently been described as one of the most rapidly evolving insect body parts. Within the Drosophila melanogaster subgroup, D. simulans and D. mauritiana only diverged 240,000 years ago, yet exhibit striking differences in the morphology of male genitalia. Periphallic structures such as the epandrial posterior lobes, surstyli and cercus, are not directly associated with sperm transfer, but vary strikingly in shape and size across the D. melanogaster subgroup. Previous studies have focused on identifying quantitative trait loci (QTLs) associated to periphallic genitalia variation by backcrossing multiple times between interspecific and intraspecific D. melanogaster subgroup species and strains. This has led to the identification of many regions across all chromosomes, bar chromosome four, linked to the diversification of epandrial posterior lobes, cercus and surstyli shape, size, and bristle features, in respect to the latter two. As the resolution of QTLs has increased, studies have now focused on functionally testing candidate genes to observe their role, if any, in male genitalia development and evolution. Following this, significant effect genes have then been studied to identify how their regulation differs between species leading to the diversification of periphallic structures. Data like this is essential for modelling gene regulatory networks (GRNs) underpinning male genitalia developmental divergence. Prior to this, my rotation project identified 49 differentially expressed transcription factors between the male developing terminalia of D. mauritiana and D. simulans, in which five were studied further for regulatory differences between the two species. The aim of this project is to build on this, to better understand GRNs that coordinate male genitalia development and evolution.