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Descripción
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| Increasing evidence indicates that viruses are widespread and highly diverse in wild ecosystems. Most of the virus species present in wild ecosystems however, remain uncharacterized. Moreover, in these ecosystems the factors affecting plant virus infection risk and population genetic diversity, two traits linked to virus emergence, are largely unknown. This thesis analyses the ecological determinants of plant virus infection risk and population genetic diversity in wild ecosystems. The thesis focuses on virus species of the genus Potyvirus present in the two most representative wild ecosystems in the centre of the Iberian Peninsula: riparian and evergreen oak forests. These analyses are based on a detailed characterization of these wild ecosystems and of the potyviruses that populate them: along three years, potyvirus prevalence (as a measure if infection risk), and seasonal data about ecological and climatic factors, were recorded in locations of both wild ecosystems. The ecological determinants affecting the prevalence and population genetic diversity of potyviruses were identified at different taxonomical scales (genus vs. species) and considering different virus life-history strategies (specialist vs. generalist). Comparative analyses of potyvirus prevalence between ecosystems indicated that virus prevalence was generally higher in riparian forests, which was associated with higher plant species richness and abundance of host plants, most of which were perennial species. This result is in agreement with theories predicting that the identity of the species present in an ecosystem, and not only the number of species, is a key factor in determining pathogen infection risk. Further analysis reported in this thesis supports this result. For instance, analyses of the association between the ecological/climatic factors and the potyvirus prevalence within each ecosystem identified the plant community composition, the host relative abundance and the host density as the most important determinants of potyvirus prevalence in the two studied ecosystems. A fine study of the role of these ecological factors in potyvirus prevalence/infection risk revealed that they are involved in different stages of virus emergence: the plant community composition would determine the risk of potyvirus jump into the ecosystem. Once introduced in the ecosystem, host relative abundance/density would affect potyvirus invasion, likely affecting plant-to-plant transmission, and thus determining the extent of the infection (prevalence) in the host populations. Interestingly, the host range of each potyvirus species appears to determine the relative importance of each of these ecological factors: host density was the chief predictor of the prevalence of a specialist virus, and host relative abundance was the major determinant of the prevalence of a generalist virus. | |
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Internacional
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Si |
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ISBN
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Tipo de Tesis
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Doctoral |
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Calificación
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Sobresaliente cum laude |
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Fecha
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16/07/2018 |