Bartonia

Abstract: Pollen morphology of the saprophytic genera Bartonia, Cotylanthera, Leiphaimos, Obolaria, Voyria, and Voyriella (Gentianaceae) was studied by light and electron microscopy. Bartonia, Obolaria, and Cotylanthera are similar in fine structure, although the exine of the first two genera is reticulate and smooth in the latter genus. Leiphaimos and Voyria are indistinguishable but markedly different from all the other genera. Voyriella does not resemble Voyria or Leiphaimos, but appears similar to genera such as Curtia or Enicostema of Gilg's subtribe Gentianeae-Erythraeinae. Considerable intraspecific variation was noted within some of the taxa.

Abstract: Taxonomic problems in Mentzelia section Bartonia (Loasaceae) are addressed using phylogeny reconstructions based on nuclear ribosomal DNA sequences from the ITS and ETS regions. Our results indicate sect. Bartonia is monophyletic and consists of two well-supported, species-rich clades. One of these two deepest clades consists of the Great Plains M. decapetala and a group of species centered in the North American intermountain region that have been described as subshrubby; whereas, the second deepest clade is more widespread and includes taxa from the Chihuahuan and Sonoran deserts as well as the Great Plains, Rocky Mountains, and intermountain region. Hypothesis tests applying the Shimodaira-Hasegawa (SH) test and Bayes factors (BF) rejected unequivocally the monophyly of (1) the ‘subshrubby’ group, suggesting multiple origins of the ‘subshrubby’ form; (2) M. multicaulis s. l., which consists of disparate clades we propose as separate species; and (3) M. multiflora s. l., which was recovered as h...

Abstract: Aim Aridification of western North America from the Miocene to the Recent has spurred plant migrations, as species invaded and/or diversified into newly formed floristic regions. The 51 species of Mentzelia section Bartonia (Loasaceae) inhabit most of these regions, providing an opportunity to investigate lineage-specific diversification among the western floras. Lineage-specific formation of the modern western North American flora was investigated by applying statistical phylogenetic methods to molecular data. Location Western North America, including the intermountain region, south-western deserts, Rocky Mountains and North American Prairies Province. Methods Internal and external transcribed spacer region data for all taxa in section Bartonia and outgroups were analysed with maximum likelihood and Bayesian inference methods for phylogenetic relationships. Distribution and phylogenetic data were then analysed by Bayesian, maximum likelihood, parsimony, and stochastic mapping optimization methods for inference of biogeographical transitions among floristic regions. Model fitting was used to assess the symmetry of transitions from mesic to arid environments. Results Multiple transitions were inferred, especially those associated with the Colorado Plateau and the Rocky Mountains. The ancestral area for section Bartonia was estimated equivocally to be all regions except the Great Basin in parsimony reconstructions, but to be the Colorado Plateau with highest probability with the Bayesian approach. Throughout these regions, transitions between mesic to arid habitats were consistent with expectations under a null model, suggesting no directional bias in transitions. In section Bartonia, within-region diversification occurred in all areas except the Great Basin and Sonoran Desert, the diversity of which is explained as the result of movement into these regions. Main conclusions The floristic regions of western North America have exchanged numerous migrants throughout their history. Among them, the Colorado Plateau, Great Basin and Rocky Mountains were particularly important floristic sources and recipients of migrants. Although previous studies have revealed a strong association among the south-western deserts, these results suggest that the plant diversities in these deserts can be influenced more by adjacent provinces than by each other.

Abstract: Three new species and two new varieties of Mentzelia belonging to the multistemmed subshrub group of section Bartonia are described. Typical of the group, they are narrow endemics occurring in relatively barren clay soils in the Intermountain Region of interior western U.S. Mentzelia tiehmii and Mentzelia argillicola are from Nevada, Mentzelia memorabalis from northern Arizona, Mentzelia multicaulis variety uintahensis from northeastern Utah and northwestern Colorado, and Mentzelia multicaulis variety flumensevera from central Utah. Communicating Editor: Aaron Liston