Image: Astatotilapia calliptera “kisiba/masoko” male and female, with the male harbouring egg-spots in the anal fin – a sexually selected male pigmentation ornament. Figure by PhD student Aaron Hickey.

Genomic basis of sexual dimorphism, sexual conflict and male ornament variation

Supervisor: Dr Emília Santos

Co-supervisor: Dr Judith Mank

One of the enduring challenges in evolutionary biology is understanding how organisms adapt and diversify in their surrounding environments. This issue has been recognized as a significant scientific challenge of the 21st century, particularly in light of ongoing environmental changes. Sexual selection plays a profound role in the process of adaptation, giving rise to extraordinary sexually dimorphic traits observed in various species, such as the vibrant peacock tail, and majestic deer antlers. These sexually dimorphic traits represent some of the most remarkable within-species variation and arise from a genome that is largely shared between males and females. Conflicts between males and females can arise due to divergent reproductive fitness or survival optima for each sex and have profound implications for genome and trait evolution. For instance, alleles that may confer reproductive fitness advantages to one sex (e.g., male nuptial colouration) may be detrimental for the other (e.g., increased predation for females). In such cases, selection acts in opposing directions on the sexes, a situation referred to as sexual conflict or sexual antagonism. There is much debate as to how sexual conflict affects adaptive potential. Such conflict can influence the ability of populations to adapt towards optimal trait values hindering adaptation. However, it has also been hypothesised that it can contribute to an increase or maintenance of genetic and phenotypic variation through balancing selection thereby enhancing adaptive capacity in an ever-changing world.

Understanding the genetic and ecological basis of sexual conflict is thus crucial to elucidate its contribution to adaptive trait evolution and the potential constraints it imposes on populations. Yet, the precise mechanisms by which a shared genome encodes substantially distinct sexual phenotypes remain largely unexplored, despite their fundamental importance in shaping differences within and between the sexes and influencing the dynamics of sexual conflict. Further, only a limited number of sexually antagonistic alleles have been identified, in large part because doing so requires understanding fitness costs and benefits in both sexes. 

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