Comparative Seed Morphology and Phylogenetics : Case Studies in Basal Angiosperms (ANITA) and Asterids (Lysimachia, Ericales)
Sammanfattning: The first half of the thesis deals with the seed morphology of members of the ANITA grade at the base of the angiosperm phylogeny (Amborella, Nymphaeales, Illiciales, Trimeniaceae, and Austrobaileyaceae), especially Illiciaceae and Schisandraceae. Seed characters support a major division between the New World and Old World species of Illicium. Fossil seeds previously assigned to Illiciaceae were re-evaluated. In Schisandraceae, seed and leaf epidermal characters were added to a previously published morphological data matrix. Phylogenetic analysis using the extended data matrix shows that Kadsura and Schisandra appear to be supported as monophyletic sister taxa by a number of synapomorphies in reproductive and vegetative characters. Fossil seeds from the Eocene of North America show some similarities to the modern Schisandra glabra from North America, whereas fossils from Europe are more similar to modern Asian species. In the second half of the thesis, seed morphology of Lysimachia and closely related taxa (Anagallis, Ardisiandra, Asterolinon, Glaux, Pelletiera, Trientalis) was investigated. The phylogenetic relationships among the endemic Hawaiian species of Lysimachia was also studied, using nuclear ribosomal DNA (ETS, ITS) and chloroplast DNA (rpl16, rpl20-rps12, rps16, trnH-psbA, trnS-G) sequence data. The seeds in Lysimachia and related taxa vary in, e.g., shape, seed coat structure and surface patterns. Seed surface patterns are mostly congruent with molecular phylogenetic relationships. A reticulate surface pattern is diagnostic for, e.g., the subgenus Palladia and the Hawaiian endemic subgenus Lysimachiopsis. Mapping seed characters onto a recent molecular-based phylogenetic tree, reveals that they provide potentially synapomorphic character states for various subclades of Lysimachia. The phylogenetic analysis based on the combined data set using nuclear ribosomal DNA and chloroplast DNA data provides new insights into the relationships within the Hawaiian subgenus Lysimachiopsis. Here our results indicate that earlier taxonomic treatments of the group need to be partially revised.
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