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

地衣是真菌（菌生体）和绿色藻类或蓝细菌（光生体）之间的专性互利外共生体。尽管在提供碳水化合物的mycobiont的光合生物的重要性，地衣的鉴定几乎完全依赖于mycobiont的形态和化学（次生化合物）的功能。Acarosporaceae和Acarospora的成员具有假定的祖先特征状态，表明地衣化子囊菌内的基部位置。因此，对该科和属的研究可能为我们了解地衣的多样性提供必要的信息。然而，在Acarospora和Acarosporaceae中发现的形态特征也在其他属和科中发现，导致它们的不确定性。在本研究中，Acarosporaceae和Acarospora在子囊菌门内的系统发育关系将重建基于三个分子数据集。这一系统发生学将成为以下工作的框架：1）确定地衣化子囊菌内主要物种形成事件的日期，同时比较三种新的确定分歧事件的方法; 2）测试用于限制Acarosporaceae和Acarospora的传统诊断特征的有效性。在真菌王国中，大约1/5的已知现存物种是地衣化的。拟议的研究将产生一个相当大的分子数据库真菌之间的系统发育关系，特别是Acarosporaceae与其他地衣化和非地衣化子囊菌。使用DNA序列重建Acarosporaceae和Acarospora的系统发育也将回答在科和属水平上长期存在的重要系统问题，这些问题尚未使用传统工具（形态学，解剖学和化学）回答。对Acarosporaceae诊断性状的研究将有助于更好地理解该科的划分。最后，将首次估计地衣化子囊菌的主要起源日期和辐射。

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.