Titel: The Ocotea complex (Lauraceae): phylogenetic studies, biogeography and evolutionary patterns
Sprache: Englisch
Autor*in: Trofimov, Dimitrij
Schlagwörter: Botanik; Phylogenie; Morphologie; Lauraceae
Erscheinungsdatum: 2020
Tag der mündlichen Prüfung: 2020-12-18
The Ocotea complex (Lauraceae) consists of about 700 species in 18 genera, most of them from the Neotropics. Ocotea is the largest genus among the Neotropical Lauraceae and includes about 400 recognized species. Some Ocotea species are distributed in Africa, Macaronesia, Madagascar, the Mascarene and the Comoro Islands. In previous molecular phylogenetic studies, only a relatively small number of Ocotea species were examined. In these molecular studies, Ocotea has been shown to be polyphyletic, or at least paraphyletic in relation to all other genera of the Ocotea complex. A more natural phylogenetic classification was not proposed due to the large size of the genus and the plesiomorphic flower structure of the taxa currently included in Ocotea. The aim of this PhD thesis was to clarify phylogenetic lineages in the Ocotea complex as a contribution to a more natural classification, with emphasis on the bisexual Neotropical and Paleotropical Ocotea species. The phylogenetic analysis of 168 Ocotea complex species, using nuclear (ITS) and chloroplast (trnH-psbA) markers, confirmed previous studies indicating that Ocotea is paraphyletic with respect to several other Lauraceae genera. The epidermal characteristics of 115 species (including 13 taxa of Aiouea and Cinnamomum) support the
conclusion derived from DNA analyses that Ocotea is heterogeneous in its current circumscription. The shape of the stomatal subsidiary cells in the Ocotea complex species is proposed to have evolved from asymmetric to symmetrical, and from relatively wide to narrower forms.
Despite this evidence, a more natural classification of the bisexual Ocotea species is still not possible due to insufficient molecular results and uncertain morphological synapomorphies in the monophyletic groups. Only two groups that fulfilled the criteria of splitting monophyletic genera from large paraphyletic groups, i.e. the Ocotea dendrodaphne group and one of the African Ocotea groups, were reinstated as Mespilodaphne and Kuloa, respectively. Possible paleobiogeographic scenarios and dispersal pathways for the Ocotea complex species, are discussed based on my own results, previous studies of the Lauraceae fossil record, and molecular analyses, as well as historical climatology and geography.
URL: https://ediss.sub.uni-hamburg.de/handle/ediss/8932
URN: urn:nbn:de:gbv:18-ediss-91577
Dokumenttyp: Dissertation
Betreuer*in: Rohwer, Jens G.
Enthalten in den Sammlungen:Elektronische Dissertationen und Habilitationen

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