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Taxonomy |
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Current taxonomic treatments consider all 300+ species of Columnea a
single genus in the subfamily Gesnerioideae and the tribe Episcieae.
However, previous treatments have not always agreed on this. The genus
Wiehler's purpose was to move away from a classification system based
entirely on floral form, which he believed to be the result of pollinator
selection and not evolutionary history. However, the split was
controversial and later workers on Columnea did not always follow the
system. Morley, Skog, Kvist, and Smith all felt that the separate genera
were not merited and that the species were better considered a single
genus. Smith did the first molecular phylogenetic work on Columnea.
These data did not sample widely from all members of the different sections
or genera of Wiehler, but did show that all species could be considered a
single genus. Subsequent work by John L. Clark that sampled more widely
among the species of Columnea has built on these results and the best
indication to date is that all species should be treated as a single genus.
The current system is to recognize 5 sections within Columnea that
largely follow the genera of Wiehler with some species moved to different
sections. Preliminary work in my laboratory has tried to verify if the different genera of Wiehler, now treated as sections, are each monophyletic (can be traced back to a single origin). The current data indicate that although some sections appear to be traced to a single ancestor such as section Columnea, other sections may have multiple origins, such as sections Collandra and Ortholoma. Recent work by John L. Clark has shown that the closest relatives of Columnea are Neomortonia, Alloplectus, and Glossoloma although Crantzia, Corytoplectus, and Drymonia, are not too far away. Columnea is distinguished from its closest relatives on the basis of its indehiscent berry fruit, although some species may represent a transition from the fleshy dehiscent fruits of its close relatives since some species of Columnea have fruits that do seem to still dehisce, albeit perhaps tardily (C. dielsii). |
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