"Viruses are one of the most important groups of parasites affecting human and animal health, and crop production, and they make a large fraction of emerging diseases. A key characteristic of viruses is their high potential to generate genetic diversity. This characteristic provides viruses with a high capacity for adaptation to new environments, including new hosts. Adaptation to new host genotypes or species may lead to the appearance of new viral lineages or species: that is, to ‘speciation’ events. This process may result in the emergence of new viral diseases, and compromise existing disease control strategies. Therefore, understanding virus speciation may be of deep social and agronomical significance as it may provide the cues to predict and control viral disease epidemics.Despite the relevance of virus speciation to understand disease dynamics, little is known about how it happens and which are its driving factors, especially for plant viruses. This project will analyse the modes and ecological determinants of plant virus speciation. Specifically, my research will focus on the species of the genus Potyvirus infecting natural populations of Arabidopsis thaliana, and accompanying annual plant species. To address the objectives of this project, I will collect field data on potyviruses population genetic structure and epidemiology, as well as on host species ecological traits. I will analyse these data by combining molecular biology techniques with advanced statistic and state-of-the-art bioinformatics tools. The results of this work will be used to build a predictive model of virus emergence integrating the genetic, ecological and epidemiological data collected.The results of this research may help to understand the origin of the emergence of novel viral diseases, helping to reach the ultimate goal of developing a predictive model of viral emergence."