UC Davis

The family Asteraceae is currently divided into 50 tribes. Some tribes, such as the marigold and thoroughwort tribes (Tageteae and Eupatorieae, respectively), include species that are native to the New World. Tageteae is more diverse and abundant in the xeric regions of Mexico and adjacent Southwest USA and includes species such as the marigolds (Tagetes spp.) and Dahlberg daisies (Thymophylla tenuiloba). Several other species have been used as medicines, spices, and garden ornamentals. Most members of Tageteae are characterized by the presence of secretory cavities in the foliage, which stored ethereal oils. Eupatorieae has two main centers of diversity, one in South America and another in Mexico, where it is especially well developed in temperate forests. It includes species that have been used in traditional medicine and as garden ornamentals, as well as Stevia rebaudiana, is the source of a sugar substitute. Species of Eupatorieae are characterized by discoid capitula and their often showy style branches.In the research documented in this dissertation, a variety of systematic studies using molecular data were conducted. In Chapter One, phylogenetic relationships, divergence time, and ancestral ranges of the genera Adenophyllum and Thymophylla (Tageteae) are estimated using nrDNA (ITS and ETS) and cpDNA (trnL-F spacer, ndhI gene and ndhI-ndhG spacer, and psbA-trnH spacer). The results support the transfer of two species of Adenophyllum to Boeberastrum, the segregation of two new genera, Adenophylloides and Thymophyllastrum, and the transfer of Strotheria gypsophila to Thymophylla. Chapter Two presents phylogenetic analyses, divergence times, and ancestral character state estimation of the secretory cavities of Tageteae sensu lato, using ITS and ETS data. Also, the sclerification of the anther appendages in the tribe is studied. Tageteae sensu lato is resolved as paraphyletic and based on the phylogenies estimated, the secretory cavities probably evolved once and were subsequently lost in at least one descendant node. Most species of Tageteae sensu lato have strongly sclerified anther appendages, but the sclerification is also found in representatives of the tribes Bahieae, Chaenactideae, and Heliantheae. Future phylogenetic and divergence time analyses of Tageteae sensu lato should consider using cpDNA data and include more outgroups. In Chapter Three, a phylogeny of marigolds (Tagetes) is estimated using ITS data and sampling almost 50% of the species. The results support the monophyly of Tagetes and its sister relationship to Hydropectis. It is desirable to conduct additional phylogenetic analyses using more molecular data, especially cpDNA, and including the species of Tagetes that were not available in this study. Finally, in Chapter Four, phylogenetic analyses of the plumeweeds (Carminatia, Eupatorieae) based on ITS, ETS, and psbA-trnH data, are presented. The results support the monophyly of the genus and the description of a new species, Carminatia balsana, which is confined to tropical deciduous forests of the Balsas Basin in Mexico. A taxonomic revision of the genus including taxonomic keys, descriptions, pictures, add distribution maps is rendered. This dissertation represents an important contribution to the systematics of tribes Tageteae and Eupatorieae of the large family Asteraceae. Each chapter also provides recommendations for future research on these groups.