Lee Poulsen
Sun, 03 Feb 2013 19:35:53 PST
One thing that seems pretty apparent to amateur me is that the DNA sequencing techniques can tell you how related two or more species are to each other, and conversely, how distantly related other species are. But other than general groupings of closely related species, or separations of species that are more distantly related than was thought, how a given set of species ought to be taxonofied into genera or families or separate species (or into the same species), I think, is still going to be something of an art that botanists will need to keep working at (and arguing about). 

One of the things I think the molecular information is really good at is in separating out and putting into the correct group those ambiguous species that one botanist thinks belongs to one genus and another botanist years later thinks belongs to a different genus, and no one really knows for sure. One recent example I learned about is Pyrolirion. It seems that for years it was thought to maybe be related to the Zephyranthes/Habranthuses or even actually be in one of those genera. But recently, DNA evidence has shown, as the wiki states, "that it is a member of the Eustephieae tribe, sister to Chlidanthus, Eustephia, and Hieronymiella." Which is very interesting given that the South American amaryllids divide up into two separate clades, the Hippeastroids and the Andean tetraploids. So Pyrolirion turns out to not be a Hippeastroid, but a part of the other clade.

And an example, that hasn't been decided yet, of how DNA can indicate relationship, but not necessarily species or genus, is the South American amaryllid example I mentioned a week or two ago regarding Paramongaia weberbaueri et al. If you see a photo of Clinanthus viridiflorus flowers, you might think it is some kind of Paramongaia species, except that it also looks kind of like other Clinanthuses. There is a new species of Paramongaia whose flowers looks like they are a 50-50 morph between a Paramongaia weberbaueri and a Clinanthus viridiflorus (in both the shape and coloring of the flowers). It turns out that DNA information indicates that these 3 species and Clinanthus mirabilis are all closely related to each other and then next closely related to all the other Clinanthuses. So a decision has to be made on whether to lump all 4 into just Clinanthus (including, yes, Paramongaia weberbaueri) [which I find my mind saying no-o-o-o-o…], or to take the two Clinanthuses out of that genus and lump them all together into their own genus (which you might think would then be Paramongaia, but priority rules would cause it to be called Callithauma) [yuck  :-) ] which would be a sister genus to Clinanthus. Or, maybe we need to start using trinomials and explicitly list subgenus, so that P. weberbaueri could become something like Clinanthus paramongaia weberbaeuri. Which I would like because then the 4 Callithaumas would have the same subgenus name, meaning they were closely related to each other, but I would also know that they were related, but not as closely, to all the other Clinanthuses.

--Lee Poulsen
Pasadena, California, USA - USDA Zone 10a
Latitude 34°N, Altitude 1150 ft/350 m

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