Systematics Section / ASPT
Mathews, Katherine Gould , York, Emily .
Relationships in Bartonia (Gentianaceae-Gentianeae) determined by nuclear and chloroplast DNA sequences, with reference to morphology.
Bartonia Muhl. (Gentianaceae), commonly known as screwstem, is a genus of four diminutive, herbaceous species distributed throughout the eastern United States and Canada. They are presumed to be wholly or partially dependent on mycorrhizal fungi due to their reduced, scale-like leaves, often purplish stems, minimal root systems, and tendancy to grow in low-nutrient environments such as sphagnum bogs and vegetation islands on rock outcrops. Our goal was to determine the evolutionary relationships among the species of Bartonia using molecular data and to re-examine a previous morphology-based hypothesis of their relationships with a molecular phylogeny. Bartonia verna, the only spring-flowering member of the genus, has unique morphological characteristics, including conspicuously long, free corolla lobes atop a short tube, and has been hypothesized to be basal in the genus. The other three species have much shorter corollas and shorter free corolla lobes. Phylogenetic analyses were based on sequences from the internal transcribed spacer (ITS) region of nuclear ribosomal DNA and from the chloroplast DNA region containing both the trnL intron and the trnL-trnF intergenic spacer. Outgroup species were chosen from members of tribe Gentianeae, subtribes Swertiinae and Gentianinae. A single most-parsimonious tree was returned in separate and combined analyses. The tree shows strong bootstrap support for a monophyletic Bartonia and for sister group relationships between B. virginica and B. verna, as well as between B. paniculata and B. texana. Bartonia virginica and B. verna share opposite to subopposite leaves and capsular dehiscence below the persistent style (“medial dehiscence”) while B. texana and B. paniculata share alternate leaves and apical capsule dehiscence. According to these results, the unique characteristics of B. verna appear to be derived and not ancestral as previously hypothesized.
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1 - Western Carolina University, Department of Biology, 132 Natural Science Building, Cullowhee, North Carolina, 28723, USA
2 - Western Carolina University, Department of Biology, 132 Natural Science Building, Cullowhee, NC, 28723, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Stevens 2/Hilton
Date: Tuesday, July 10th, 2007
Time: 3:45 PM