Scottish Rock Garden Club Forum
Specific Families and Genera => Primula => Topic started by: Giles on July 15, 2008, 11:17:02 PM
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-have any of you read this article in the current American Primrose Society Quarterly 'Primroses' ??
-about the transfer of Dodecatheon species to the Genus Primula?
Any thoughts??
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Oh NO! How could they?
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methinks:
European Primulas: friendly, reliable.
Asiatic Primulas: exquisite,tempting.
Dodecatheon: '***********'
Would you take green tea with a 'Big Mac' ?
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Would you take green tea with a 'Big Mac' ?
Actually, Ian would do just that! ::)
Paper on transfer of Dodecatheon to Primula is available free :
www.botany.wisc.edu/courses/botany_940/11JClub/MastReveal2007.pdf (http://www.botany.wisc.edu/courses/botany_940/11JClub/MastReveal2007.pdf)
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As I get older I find there are too many names to remember ...... lets make things simpler :o
(only joking of course!)
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I like to consider myself to be a discriminating consumer of taxonomic information. So, when a proposal to change a name comes along, I like to delve in to the data and try to understand why the name change is being proposed.
In the case of Dodecatheon, the change to Primula is advocated by people who believe that all taxa (families, genera, and species) should be monophyletic, that is, include all of the descendants of a common ancestor. Since Dodecatheon has evolved from within the genus Primula, strict "cladists" require all species of Dodecatheon to be transferred to Primula. Recognizing Dodecatheon as separate from Primula involved the recognition of paraphyletic taxa. However, the code of botanical nomenclature does not require all taxa to be monophyletic, so not everybody is in agreement that this rule must be followed. Another, more familiar example of a paraphyletic taxon are the dinosaurs, that is, if you don't call birds dinosaurs. Since birds evolved from dinosaurs, strict adherence to monophyly would require birds to be called dinosaurs.
A recent issue of the NARGS journal had a nice article about Dodecatheon and how it has evolved from Primula by Jim Reveal. Reveal is an adherent of the principle of monophyly, so he advocates for calling shooting stars primroses, but it is still an interesting article to read.
I plan to still use the genus name Dodecatheon.
Ed
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Ed, you should have ended your post with "Have a happy day!"
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Ed,
You have put your finger on a rather vexed question. The same thing has happened to Hebe the genus being recently subsumed back into Veronica. While one could accept returning the smaller semi-herbaceous Parahebes to Veronica it is more difficult to accept returning the shrubby species to Veronica. It seems to me that despite Hebe and Veronica or Primula and Dodecatheon being monophyletic it would appear that some groups have diversified and moved on in evolutionary terms. So when looking at a monophyletic clade some members have changed little from the progenitors of the group while others have changed dramatically to the point where they appear quite distinct and are recognized as separate genera by traditional taxonomists.
Not withstanding I do not think there will be any rapid resolution of some of these issues. Also one is entitled to use any validly published name provide you cite the authority ie Dodecatheon meadiaL.
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Howdy,
My name is Adam Monophylecticus and I live in the country Country and I grow the plant 'Plant' and I am accompanied by the animal 'Animal' ;D
The way we normally describe plants and animals is that we have groups that contain several subgroups. Primulaceae containing Primula, Dodecatheon, Dionysia, Douglasia etc etc. This is a practical picture but would not describe the probable ancestry correctly. However, it serves the practical purpose of definition and does give good hints about relationships.
It is not so that a Protoprimulace originalis suddenly and parallely splits into Protoprimula communis, Protododdecatheon communis, Protodionysia communis etc. Nor is it so that Protoprimula communis suddenly and at one time split into Primula veris, P elatior, P auricula etc.
The splits come forklike. Protoprimulacea communis split into Protoprimula communis and Protodionysia communis, Protoprimula communis then split into Protoprimula communis and Protododecatheon communis. Then it split off Protoprimula veris which split off Pp elatior. (Note this is a hypothetical description for the sake of argument. I am not saying that I know that this is the order of splits)
As I understand the situation (and I might be all be wrong) The reasoning behind merging Dodecatheon into Primula is that it split off later than some "true" Primulas. It is not enough that they have a common ancestor. If that were enough we would have to put all species of the world into one genus and one family.
As I see it this argument can be contested for several reasons.
#1: Names are labels used for identification. In the phonebook you will find August Andersson next to Augusta Andersson even if they are not related and have never met. Nobody considers the phonebook wrong for that reason. Nobody would suggest that the order in the phonebook should be after relationship.
#2: It would make quite as much logical sense to rise the Primula sections auricula, sikkimensis etc. into genera and keep Dodecatheon as such.
#3: If Dodecatheon as a group is distinct enough from the members of the genus Primula they should deserve generic status. I think that is the case.
#4: Strict cladism would destroy our present system entirely. We would have a new subgroup for each split. No Order would have more than two families, no family would have more than two genera. We would then have to revise the whole system every time someone finds a new gene somewhere.
It all boils down to: how much distance that signifies that there are two groups; be they genera, species or families. The world is not all that clearcut. Ranzania japonica is very distinct from all its relatives. Enough to form a separate genus and species. It sits nicely in its little box. Trilliums erectum, flexipes, simile, vasyeii etc have all sorts of intermediate forms. They float around. Some people say that they are all the same variable species. Some say that there is the ideal erectum and the ideal flexipes out there like holy grails and that all other forms (making up 95% or more) are mongrels.
For these reasons I will also go on using the word Dodecatheon. ;D
Göte
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Gote,
You raise some interesting points some of which I support others not entirely.
Names are not just "tags" they do serve to indicate relationship or similarity and common ancestry is the most powerful measure of a relationship between different individuals and by extrapolation different species. This is the rational for constructing phylogenetic trees based on the analysis of gene sequences. Plants have a nuclear genome inherited from both parents, and a chloroplast genome that is inherited from the female parent so often sequences from both nuclear and chloroplast genes are analysed for taxonomic purposes. In some cases they produce different phylogenies. The qualification of all of this is that you are looking at relationships between the genes you are studying when you construct phylogenetic trees. Genes do not necessarily accumulate changes at uniform rates so it is difficult to time splits with any confidence from genetic data alone.
The other difficulty is ranking taxa ie do three nucleotide changes indicate a species or eight a generic split?
I agree with the point that in some cases you can resolve these problems by raising subgroup to generic status. However again I agree that strict cladism would in some measure destroy the utility of any taxonomic system - a Dodecatheon is a Dodecatheon because it has distinctive morphological features that differentiate it from the rest of the Primulaceae.
I think that DNA taxonomy is useful in placing related species in the appropriate genus but where it is used to define rankings between/within genera problems arise.
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Dear Gote and David,
If you were not very nice men, as I know you both are, and if I were a very rude person (which I can be but generally am not) I would say to you both, what my partner Roger says to me when he thinks I'm talking nonsense: "Go boil your head!"
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Dear all :)
It has been interesting to read Your views and ideas around and about this subject.
I learned a lot.
Kind regards
Joakim
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David,
It has been proposed to let the name of a plant or animal include all classes and Thus let all plant names look like:
Plantae-Magnoliophyta-Rosidae-Sapindales-Aceraceae-Acer-saccharum
To make it even more palatable it should be reducede to acronymes so that the sugar maple would be called:
PlMaRoSaAcAcesa.
It was further proposed that in the name of computation (This was some time ago) the letters should be replaced by numbers.
I do not think that all names should be labels only. However, I would not like a mess like the one above described.
I do not disagree with you that plants names should as far as practical reflect relationship.
However, A name as Saxifragaceae is a label since all genera are not closely related.
Dear Lesley,
Does this mean that you are a phylogeniholic??
Or is it Roger who is one?
;D
Göte
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Gote,
It has always seemed to me that the genus species concept is the core of the Linnean system of classification. The fact that the Saxifragaceae are polyphyletic can be sorted out by reassigning the constituent genera to the appropriate family. Our Hebes have been shifted to the Plantaginaceae by recent authors. One can be consoled by the fact that despite being weeds Plantago is a very successful genus.
However a stable classification is important for very practical reasons especially for horticulturalists. It is inconvenient to have plants shuffled around between different genera and families etc on the apparent whim of academic taxonomists. So from my own point of view it is easier to accept some changes but not others and I suspect I am not alone in this.
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Very true David. What I now realize is that this whole topic was introduced for the purpose of giving us a good laugh.
Last night we had cream and PlMaRoSaAcAcesasy on pancakes, for dessert!
As to your question Gote, I can only answer yes, or no, or maybe.
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I am about to disregard the prime rule for posting on this forum ie lets not spoil a good barney by introducing facts.
I took the rash step of looking up the papers around which this discussion revolves. The formal transfer of Dodecatheon to Primula was done by Austin R Mast and James L Reveal in a publication called Brittonia in 2007. In an earlier 2004 publication in the American Journal of Botany, Mast and his collaborators present a genetic analysis that shows that the genus Dodecatheon is most closely related to Primula suffrutescens from Western North America. The point is made that Primula parryi (another Western North American species) is virtually indistinguishable from Dodecatheon jeffreyi "when the corollas and inserted anthers are removed".
The conclusion is that Dodecatheon evolved from Primula in Western North America.
The authors then consider how the Dodecatheon flower arose from an ancestral Primula flower. Basically they propose that it involved modification of the pin/thrum determinant genes with additional changes to produce the characteristic Dodecatheon flower morphology ie changes in relatively few genes affecting flower morphology. This gives rise the so called " Buzz-pollinated flower " of Dodecatheon so the net result is a change in the pollination system. In evolutionary terms Dodecatheon flowers evolved to support/respond to different pollinators.
So where does all this leave us; Dodecatheons are specialised North American Primulas that evolved a different pollination system. The same type of pollination system arose independently in Cyclamen.
Lesley, I hope that now you have mastered the system you would not mistakenly grab the bottle of PlMaRoEuEuRiCo to have with your pancakes and cream. ;D
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Sorry for a maybe stupid question:
Is not the pollination system of such importance that it is used to separate families as well as species? For orchids of Opfrys type there is suggestions that every different pollinator makes the flower different enough to make it a species. Maybe a bit of an over-kill but still the point of a (very?) different would make the difference obvious or?
Hence I would not understand why the authors put them as same family.
Kind regards
Joakim
PS Reading reference articles are considered as cheating in some circles ::)
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OOh, it is a good barney! Does that mean cyclamen should be renamed primulas too? ??? ???
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Anne or the argument is that since they did not renamed Cyclamen they should not have renamed Dodecatheon. At least if I understood David correctly.
Please correct me if I got it all wrong.
Kind regards
Joakim
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I'm changing my name
- and emigrating.......
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To what genus?
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I love plant names...and the process. It's fascinating...and unending source of discussion material.
In the end, however, I grow what I'm interested in--and take a fancy to--and the name is a secondary consideration. I have BOTH primula and dodecatheon in the gardens, as I suspect many on this forum do. I try to keep my records reasonably current and accurate as far as names go, but will be keeping dodecatheon for the time being, just as I kept chrysanthemum until the genus was, more or less, put back together...
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Lesley, I hope that now you have mastered the system you would not mistakenly grab the bottle of PlMaRoEuEuRiCo to have with your pancakes and cream. ;D
Well you know me David, I'll drink anything - once!
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Joakim,
In traditional taxonomy that relies on morphological features for classification flower structure is very important in in determining species genus family etc. The assumption is that structure of the reproductive parts is less plastic than other characters such as leaf shape and which can vary due to adaptations to the environment ie as in xerophytic leaves. When genetic analysis reveals a relationship that is at odds with that arrived at by more traditional methods (floral morphology)then these contradictions need to be reconciled. The authors of the Dodecatheon paper have in fact done this by re-interpreting the structure of the Dodecatheon flower in terms of its relationship to the more typical Primula flower. Their conclusion is that Dodecatheons are a group of Primulas that have evolved a specialised pollination system and the flower structure you recognize as a Dodecatheon is a consequence of this change.
As modern methods of genetic analysis become powerful and widely employed there will doubtless be further " upsets " to current views.
Anne,
There is no compelling reason to subsume Cyclamen into Primula: I am assuming the split between the two genera occurred prior to the Primula diversifying to the extent we see today and the two genera are now genetically more distant. A similar change in floral morphology to that leading to Dodecatheon would have occurred in the most recent common ancestor of Cylamen and Primula leading to Cyclamen.
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David thanks for the information. It is nice to learn more.
Kind regards
Joakim
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The last few papers on Cyclamen place it in the Myrsinaceae (in the Primulales) with Lysimachia! It's a good thing I know of no one (private gardener) that writes the family on a label also.
Reveal's paper was available on the internet for free most of last year. It may still be.
Aaron Floden
Knoxville, TN
edit :
Paper on transfer of Dodecatheon to Primula is available free :
www.botany.wisc.edu/courses/botany_940/11JClub/MastReveal2007.pdf (http://www.botany.wisc.edu/courses/botany_940/11JClub/MastReveal2007.pdf)