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Freie Universität Berlin (2019)

Systematics and evolution of Gomphrena (Amaranthaceae) with an emphasis on the species in Bolivia

Ortuño Limarino, Teresa Dunia Isab

Titre : Systematics and evolution of Gomphrena (Amaranthaceae) with an emphasis on the species in Bolivia

Auteur : Ortuño Limarino, Teresa Dunia Isab

Université de soutenance : Freie Universität Berlin

Grade : Doktors der Naturwissenschaften (Dr. rer. nat.) 2019

Résumé partiel
The dissertation investigates Gomphrena L. and allied genera with morphological and molecular data in order to test the phylogenetic relationships and to better understand the evolutionary history of this linage. An emphasis is on the actual Gomphrena clade and as well the diversity in Bolivia. Gomphrena (Gomphrenoideae) is the largest genus of the Amaranthaceae with an estimated number of 120 species. The areas of main diversity of this genus comprise South America with about two thirds of the species, Central and North America (about 15%), and Australia (about 20%). This genus largely grows in tropical climates. Some of the species are used as medicinal plants, and a few are cultivated as ornamental plants exhibiting attractive pigmentation in their tepals. The first chapter presents the state of knowledge and a general introduction into Gomphrena. It is important to note that previous molecular phylogenetic studies revealed that Gomphrena in the widely used circumscription of Schinz (1934) is a polyphyletic group. These past studies included only few species of Gomphrena and distinguished two main clades. The first clade includes the type species of the genus, G. globosa L., and certain Australian and American species, plus the allied genera Gossypianthus Hook., Lithophila Sw., and Philoxerus R.Br. (= Blutaparon Raf.) with not fully understood relationships. This group of Gomphrena s. str. is here called “Gomphrena clade” whereas the second group that includes G. elegans Mart., G. mandonii R.E.Fr. and others is part of a lineage called Pfaffia clade (not studied here). In addition, the first chapter presents the complex taxonomic history of Gomphrena. The second chapter focuses on the morphological characteristics of the Gomphrena clade. As a result 22 vegetative and floral morphological characters were defined with their respective states and assessed for 27 representative samples. The photosynthesis type (absence or presence of C 4 photosynthesis) was coded in the form of a single trait including morpho-anatomical characteristics. For chapter three a combined data set of chloroplast sequences (matK-trnK + trnL-F + rpl16) of the Gomphrena clade (including the allied segregate genera) and outgroups from Gomphrenoideae was analyzed with parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) methods. The 22 morphological characters were optimized on the Bayesian Maximum clade credibility tree using Bayes Traits. The results show that most vegetative characters including the annual life form have evolved multiple times, whereas some floral character states were identified as synapomorphies. An important result reveals that many of the nine characters defined for the androecium, most of which were used historically for the pre- phylogenetic delimitation of Gomphrena and other genera, appear homoplastic.

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