Dissertation Research: Phylogeny, Reconstruction of Ancestral States and Divergence Times of the Lichen-forming Fungi Acarosporaceae and Acarospora

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Lichens are obligate mutualistic ectosymbioses between fungi (mycobionts), and green algae or cyanobacteria (photobionts). Despite the importance of the photobiont in providing carbohydrates to the mycobiont, the identification of lichens relies almost exclusively on morphological and chemical (secondary compounds) features of the mycobiont. Members of Acarosporaceae and Acarospora have putative ancestral character states suggesting a basal position within the lichenized ascomycetes. Therefore, the study of this family and genus is likely to provide information essential to our understanding of the diversification of lichens. However, morphological features found in Acarospora and Acarosporaceae are also found in other genera and families, resulting in their uncertain circumscriptions. In the present study, phylogenetic relationships of the Acarosporaceae and Acarospora within the Ascomycota will be reconstructed based on three molecular data sets. This phylogeny will be the framework to: 1) date major speciation events within the lichenized ascomycetes, while comparing three new methods for dating divergence events; and 2) test the validity of traditional diagnostic features used to circumscribe Acarosporaceae and Acarospora. About 1/5 of all known extant species in the fungi kingdom are lichenized. The proposed research will generate a considerable molecular database relevant to phylogenetic relationships among fungi, in particular of the Acarosporaceae with other lichenized and non-lichenized ascomycetes. The use of DNA sequences to reconstruct the phylogeny of the Acarosporaceae and Acarospora will also answer long-standing and important systematic questions at the family and genus levels, that have not yet been answered using traditional tools (morphology, anatomy and chemistry). The study of Acarosporaceae diagnostic characters will contribute to a better understanding of the delimitation of the family. Finally, major dates of origin and radiation of lichenized ascomycetes will be estimated for the first time.