Infrageneric classification in Ribes has previously relied on a few, often
conflicting, morphological markers, such as spines, glands, and inflorescence
morphology. Suggestions that hybridization drives the evolution of the genus have
not been tested using phylogenetic methods. To assess the validity of infrageneric
classifications and the importance of hybridization to the evolution of the group, and
to develop an explicit phylogenetic hypothesis, I surveyed exemplars from all
subgenera for restriction site variation in two cpDNA regions. Parsimony analysis
shows that red currants, European alpine currants, golden currants, true gooseberries,
and western gooseberries appear on separate clades. A less well supported Glade
includes the western North American ornamental currant group and a portion of the
dwarf currants. The presence of distinct lineages in Ribes is strongly supported by
characters with very high consistency, suggesting that hybridization among
infrageneric groups is not common in the genus. Unexpectedly, spiny currants and
true gooseberries are united, suggesting either a sister group relationship or the
possibility that one of these groups arose by reticulate evolution. The four black
currant species examined exhibit surprisingly high divergence, and are not
monophyletic in the analysis. Maximum likelihood analysis supports these results.
Basal relationships of these lineages are not well resolved.
A similar analysis of a portion of the nuclear ribosomal repeat produced very
few characters. Although these data are highly homoplasious, their analysis bears
some resemblance to that of the chloroplast DNA. Most prominently, the ornamental
currant Glade has identical membership.
Brief reviews of the scattered palynological and paleontological literature
concerning Ribes are presented. / Graduation date: 1995
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35087 |
| Date | 18 November 1994 |
| Creators | Messinger, Wes |
| Contributors | Liston, Aaron |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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