PhD defense by Yujing Yan

Yujing Yan

Phylogeny, biogeography, and diversification of the tea family (Theaceae)

PhD defense by Yujing Yan

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Associate Professor, Michael Krabbe Borregard, Center for Macroecology, Evolution and Climate, Globe institute, University of Copenhagen
Professor Carsten Rahbek, Center for Macroecology, Evolution and Climate, Globe institute, University of Copenhagen
Assessment committee:
Associate Professor Tobias Frøslev (chair), Globe Institute, University of Copenhagen Professor Susanne Renner, Ludwig-Maximilians-Universität München, Germany Associate Professor Wolf Eiserhardt, Århus Universitet , Denmark


The distribution of life on earth is uneven between regions and taxonomic clades. It is well acknowledged that much of the uneven diversity patterns we see today are linked to the past environment and reflect the variation in the processes of speciation, movement, and extinction in deep times. However, our understanding of the relative importance of these processes remains inadequate.
In this thesis, I focused on the tea family (Theaceae) and explored factors that contribute to its macroevolutionary patterns. Researchers have been long curious about the cause of disjunctive distributions and the unbalancing species number among different groups in this family. However, many of the previous attempts in solving the problems have been hampered by the controversy within the taxonomy classification and the lack of a robust phylogeny with a complete taxon coverage. Through analysing a combination of newly generated molecular, distributional, and ecological data, I provide evidence to link the boreotropical forest to present-day subtropical forest, and indicate complex evolutionary processes driven by changing climate and evolving biota underlying the explosive diversification. The study provides a concrete basis for continued research into more detailed explorations on the relationships between environmental change, trait evolution, and species diversification of the focal group.