Many species have independently evolved similar phenotypes in response to similar environmental challenges. This phenomenon, termed convergent evolution, reflects both the power and the limits of adaptation. However, we often do not know the genetic basis of convergent evolution. This is because, until recently, it has not been possible to investigate the genomic basis of evolution in most systems, limiting our understanding of the factors that facilitate or inhibit convergence and adaptation. To fully understand convergent evolution we need to query the genomic response to selection and determine genotype-phenotype links in systems where convergent adaptation is well established. The Trinidadian guppy (Poecilia reticulata) is a system that offers the opportunity to test the roles of multiple factors in convergent evolution: this species includes multiple natural and experimentally established populations that have repeatedly evolved similar phenotypes under similar predation environments.
The aim of this project is to fully characterise the genomic-basis of repeated adaptive evolution in guppies. First we examined genomes from natural populations of guppies through out their range. We found regions of the genome that were repeatedly evolving independently in response to reduced predation. We also found the evolution was limited by geographic structuring and past population size changes. We next examined genomes of experimental established populations. Here we found loci that responding quickly to change in environments. These loci were also found to show signatures of selection over longer time periods.
Our second aim to link the phenotype to the genome through quantitative genetic approaches revealed a significant polygenic effect, where traits were due to the interaction of many genes. We are following-up these results with more fine-tuned mapping approaches, including those that target the effect of the Y chromosome.
Finally, we also generated important resources that will be used to link the phenotype to the genome through transgenic methods. Overall, our work shows how repeated selection is reflected at the genomic level, determined the genetic basis of convergent adaptations, and ultimately understand how convergent evolution has occurred in an important wild system.
