Mahurin Honors College Capstone Experience/Thesis Projects



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The genus Comus (the dogwoods) contains 50 species that have been divided into nine subgenera. One of these species, C. volkensii, has been segregated into the subgenus Ajrocrania. Previous studies combined morphological, anatomical, and chemical data to produce a hypothesis of evolutionary relationships that placed the subg. Afrocrania as a segregate lineage sister to the subg. Comus, and placed the Ajrocrania/Comus lineage sister to the big-bracted dogwoods (Murrell 1997). The subgenus Afrocrania has been examined morphologically, anatomically, and palynologically; however, it was not sequenced in Xiang's (1993) analysis of rbcL (chloroplast) sequence data, or in her analysis of the matK region of chloroplast DNA. Murrell's (1993) earlier analysis of the Internal Transcribed Spacer (ITS) region of nuclear ribosomal DNA included sequence data for C. volkensii, but these data were suspect because of inconsistencies with the sequence data for members of the subgenus Comus. Both ITS regions from the subg. Ajrocrania were amplified using the external primers 4 and 5 and the Polymerase Chain Reaction (PCR), and two distinctly migrating bands (approximately 750 bp in length) were consistently obtained. These amplified regions were cloned in an attempt to isolate these disparate bands for sequencing. Pylogenetic analyses of the sequences revealed that subgenus Afrocrania forms an unresolved trichotomy with subgenus Thelycrania (the blue- and white-fruited dogwoods) and the Dwarf dogwoods, the cornelian cherries, and the big-bracted dogwood.



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