Evolutionary, phylogenetic, and biogeographical studies within the diploid-polyploid complex Veronica subsect. Pentasepalae (Veronica L., Plantaginaceae)

Abstract

This thesis aims to decipher the contribution of polyploidization and hybridization processes to the evolutionary history of the species included within Veronica subsect. Pentasepalae. The thesis is related with three main disciplines: evolution, phylogenetics, and phylogeography. First, we reconstructed a molecular phylogeny for V. subsect. Pentasepalae based on distance methods using Amplified Fragment Length Polymorphisms (AFLPs) including all taxa recognized within the subsection, in order to understand the phylogenetic relationships among species, and to evaluate whether they are monophyletic. Furthermore, a revision of the taxonomy of the group was performed making use of an integrative approach. This thesis also attempts to improve our understanding of the implications of polyploidy in the geographical distribution of natural plant populations. To this aim, we performed the first ploidy screening within V. subsect. Pentasepalae at a global scale. The relationship between ploidy levels and environmental variables was evaluated using climatic variables, and the role of the biogeographical history of the species in the geographic distribution of cytotypes was also examined. Our last, but not least aim is to detect the biological and historical processes that shaped the evolutionary history of Veronica aragonensis, a mountain endemic species from the Iberian Peninsula. Next-generation sequencing and high-resolution melting analyses were used to characterize a new set of specific microsatellites, which were used to assess the genetic diversity and structure, and the levels of gene flow within and among populations. Genetic patterns were investigated in the three areas of distribution of V. aragonensis (i.e. Pyrenees, Pre-Pyrenees and Baetic System) in order to assess the relative contribution of range fragmentation vs. long-distance dispersal events for the current distribution of the species. In addition, we tried to identify populations that could have acted as glacial refugia for V. aragonensis during the Quaternary glaciations. Finally, we propose the most adequate strategies for the conservation of the genetic diversity of this rare and endemic taxon.