Posted: May 31 2009
Cyphoma of Florida
Sun 9/3/2017 Vicky Wall posted on Conch-L:
"When I was checking my shell labels to see if any taxonomy had
changed, one had, according to WoRMS: Cyphoma mcgintyi is now
considered Cyphoma gibbosum. I've attached an article from the
WoRMS entry that discusses the DNA studies. As stated in the
abstract, DNA studies have determined that the differing mantle
colorations observed in once considered 3 separate species of
Cyphoma are morphological varieties of a single, genetically
Bastian T. Reijnen & Sancia E.T. van der Meij. March 2, 2017 Coat of
many colours—DNA reveals polymorphism of mantle patterns and
colouration in Caribbean Cyphoma Röding, 1798 (Gastropoda,
Ovulidae). PeerJ 5:e3018. https://doi.org/10.7717/peerj.3018
"Molecular analyses based on four molecular markers (COI, 16S,
H3 and 28S) for three Cyphoma species (C. gibbosum, C. mcgintyi,
C. signatum) and an unidentified black morph, collected from three
localities in the Caribbean, show that they represent morphological
varieties of a single, genetically homogeneous species. This outcome
is in agreement with previous anatomical studies. As a result
C. mcgintyi and C. signatum are synonymised with C. gibbosum ..."
"Cyphoma gibbosum form or variety mcgintyi. Just add a new
species name and downgrade the old one and do not lose
information. Usually genetic studies discern cryptic species rather
than false distinctions, but it can go either way."
"Lot of controversy over this one. It was discussed on FB rather than
conch-L. Some say OK, many say not enough DNA proof was used in
the paper. Some (a very few) agree with the authors, most feel more
work needs to be done before changing those labels. I am sure
others will weigh in.
I am not positive, but Colin Redfern's Bahamian Seashell list of
corrections and additions may have a link to this paper. I know it is
accessable on line, as I got it. Shamed to say, read it, shouted
"Balderdash" and moved on. More work needs to be done."
I just collected four fresh specimens of C. McGintyi. They don't look
like gibbosum, don't have the colored shell of gibbosum, and have
a completely different looking mantle than gibbosum. I am not
shamed to say at all, "BS". If whoever wants to lump these together,
lumps them together, that is their business. I have been collecting
McGintyi for over 40 years. Having collected gibbosum in the Keys,
the two are different. I really don't care what someones' DNA test
says. If I put the shells side by side, alive or dead, they are not alike.
I am, for one, tired of all the "changing". They have a lot more work
to do before they convince me of their conclusions.
Collecting and collecting....I am with Carole on this one. Can you
say DNA contamination.....?
You don't need DNA contamination. They only sampled a small part of the mitochondrial DNA, and the critical part may well have not been examined. One problem is that we do not know what the critical part is...
"I wasn't sure what to do either as I have heard from other folks that WoRMS isn't the be all end all of taxonomy. I think using the word "variety" is the way to go until more data comes in. I just thought it was an interesting article."
"Dear Allen and Vicky,
Evolution of reproductive isolation can proceed at a pace exceeding that of "genetic distance."
Doug Stemke offered the following trenchant analysis of this dichotomy to this forum on Wednesday, February 20, 2013:
"I am a molecular biologist myself and teach a course in Biodiversity. I find that I have to give a balanced answer to how much weight to give DNA. The classic example is the Monk flower. A single gene apparently separates a red flower from a white flower. It may in fact come down to a single base pair in the 'red gene' or even a single base pair in the control of the gene that causes the gene to be on or off. That would hardly seem to be enough difference, from a DNA level, to justify two species. But the difference in a practical sense is red flowers get pollinated by birds (hummingbirds) white flower rely on insects to pollinate them. They do not exchange DNA. Presumably each color flower will then begin to gather separate mutations and over time will ultimately diverge. But at the point at which those two organisms are no longer mating they have become separate species. DNA in this case where an algorithm is used to identify species would potentially mislead classification whereby a Biological Species concept probably is the best way to classify a species.
Other examples of this disconnect among the Gastropoda are conversion from planktotrophy to lecithotrophy and chiral reversal. The latter is likely governed by a single gene. The discussion can be found at ]https://listserv.uga.edu/cgi-bin/wa?A2=ind1...0mindspring.com [/URL].
Whether it be "instant speciation" or "incipient" speciation (as Reijnen and van der Meij reasoned) may be moot.
Taxonomy has its limitations, but the morphospecies concept is defensible, and, as Allen points out, it has provided us a vocabulary."
"Which leaves you with the very difficult task of finding out if the differences prevent interbreeding. Do the different patterns mean they live on different substrates and thus do not interact? Are there any other differences that prevent them from getting together for breeding--like sexual selection in birds that can cause speciation when males differ in color or song."
"I agree, Allen. We have three disjunct "morphotaxa" here. Something must be restricting gene flow (or expression).
Reijnen and van der Meij addressed trophic specialization (your "different substrates") and, based on the catholic appetite of Cyphoma gibbosum, considered it an unlikely scenario. I'm not sure that conclusion is well-supported."
Bob Fales sent me an email off-list yesterday, and I answered him as best I could. He has permitted me to post the brief exchange (below) as it seems relevant
I guess that one "dumb" question might be whether or not anyone has found specimens indicating hybridization?
Not dumb, pivotal. The word "hybrid" does not appear in the paper. The authors state that each of the three principal taxa treated, "Cyphoma gibbosum, C. signatum, and C. mcgintyi, has a unique characteristic mantle pattern and colouration [sic]," which conforms to the literature and my personal observations over the years.
If I may jump in to this conversation a bit late…back in June I added a post on my Facebook Group/Blog about this article. The comments/discussions were spirited and I thought it would be good to make available these comments here on Conch-L for those not involved with F.B. The names of the commenting participants have been initialized since I did not get permission to reuse their posts. Some of you will be able to figure out who made the comments based on their initials and what they say in their expertise areas.
Copied From my “Conchology Is Shell Collecting” Group on Facebook
Posted June 15, 2017 with comments added between June 15 and August 6.
Rich G. Posted: A recent scientific paper (https://doi.org/10.7717/peerj.3018) proposes the demotion of two West Indian species of Cyphoma into synonymy of Cyphoma gibbosum based on molecular data. In short, the paper discusses the polymorphic character of the animal's mantle.
If I can play devil's advocate for a moment, many recent DNA research studies also include investigation into the morphological aspects of the mollusk's shell to give a more complete assessment of speciation, or lack of... In this case the shells of the 3 described Cyphoma and one undescribed morph are as different as the patterns of their mantles.
Certainly a multi-prong approach to taxonomy opens doors for more discussion and debate and is making me a bit "verklempt", so in the words of Mike Myers' Coffee Talk character Linda Richman, "Talk among yourselves...".
C.M. wrote: DNA!! What I know about this can be put in a thimble. But here is my limited experience. To my great shock, I just discovered my dad was not my father! Trust me it was a shock, so to ancestry dot com my brother and I sent our spit. Ancestry had us as first cousins with question marks. And with that came a list of different relatives and some same relatives. So here is My view sure all the Cyphomas share some of the same DNA, they are parts of the same "clan" . But they are more cousins than the same species. I expressed myself in this a few weeks ago, really more much more work needs to be done before we go changing labels.
P.K. wrote: This hit a cord with me, Rich. If animal and shell morphology don't distinguish a species and DNA is the marker, I guess a lot of previously named species will be lumped and some will be split. Confusing!
Rich wrote: My point exactly...
M.J.T. wrote: That is absolutely correct P.K.
R.A. wrote: I'm a rookie on this scientific part, but my humble opinion, the morphology of the shell and animal should be the first marker in separating species
M.J.T. wrote: It is the most evident marker for species separation, The problem is that the observed morphological characters are subjected to environmental adaptations (phenotypic plasticity) and might not be directly related with phylogeny. for instance, boar and pig: same species, although morphologically distinct.
P.K. wrote: Hi M.J.T., The problem as I see it is how to determine if a species morphologic differences are environmental variations. I guess in that case DNA would be the determining marker. Recently it appears that much of the species naming has been arbitrary and based on minor morphological variations.
R.A. wrote: Completely agree with you P.K.,Ii think it's the biotype of the location that sub-dived species.
M.J.T. wrote: Actually without DNA evidence, the species hypothesis remains untested. In certain groups like cone snails, it appears that radular morphology is a good proxy for phylogeny, and in any case better than shell morphology.
C.E.R. wrote: This is interesting Rich...I have always thought of these as three species especially in photographing them...If they (a species) can be this different phenotypically but the same genotypically imagine what it might do to some of the Indo-Pacific morphs...I agree with P.K. - just Wow!
C.R.A. wrote: Well, I just read the paper and I have to say the conclusion is simply unsupported. It is clear that genetic differentiation within this species complex is negligible. It would be most surprising to find otherwise. Now, the most reasonable explanation to reconcile morphological, ecological and genetic data is to consider the "morphs" as closely related, recently diverged species. The authors dismiss this with the sole reasoning that speciation should proceed through divergent trophic specialization. This is nonsense -it could be sexual selection, for example. So, in my opinion, the taxonomic conclusions are not only premature but unsupported.
Rich wrote: So then my playing devil's advocate in this situation is not at all wrong. I just feel the data lacks a holistic approach to determining speciation.
P.K. wrote: From the viewpoint of a layman, recently there seems to be no consistent formula used to justify the naming of a species.
Rich wrote: At least from the molecular land mollusk studies that I've been privy to, there needs to be a certain amount of separation in the numbers (excuse my unknowledgable terminology) to begin to determine species separation. I'm not sure how their numbers stack up with the Cyphoma studied.
C.R.A. wrote: Exactly. A species is an evolutionary lineage and we need all evidence available to sort it out. There are genera which evolve quite fast: for example, crossbills are impossible to tell apart unless one hears their calls. In this case, recent but clear speciation means very little genetic divergence. And in this case also, the driving force is not food, but kin recognition. In Cyphoma it may be any other isolating mechanism, with a comparable outcome -speciation without genetic differentiation.
F.L. wrote: Ovulids are in a constant arms race with their host. Of course, their evolution proceeds very fast, and in shallow water environments we cannot expect to find fine-tuned lineage sorting manifested in those sequences compared, especially not in closely related congeners. If we took the same approach and used it on the species of Cypraeovula, then fuscodentata, capensis and fuscorubra were all the same species.
D.P.B. wrote: There is another much more plausible answer, namely that their methods are weak at best since they only looked at a few mitochondrial DNA loci. Nuclear DNA needs to be used as well, with many more loci to better analyze the organisms under study.
M.J.T. wrote: Normally nuclear genes are more conserved at the species level, and they are more informative at supraspecific and higher levels. If mitochondrial genes do not vary, I would not anticipate a big difference if nuclear genes were included.
And the final comment received so far:
F.L. wrote: Anyway.... there has been a lot of irritation about this particular paper (and another one by this author) expressed to me in different degrees of embarrassment. Personally, I do not care because any old fashioned fool like me can see these are different species. But regardless, I personally think that the title of an article that is highly speculative (at most) must not anticipate one of many possible explanations for the data this method delivers.