New discus classification ... 5 groups!

[pcsb23]

Thought I'd share this ...

http://www.sage-hindawi.com/journals/ijeb/aip/360654.pdf

Genetic characterization of Amazonian discus fishes of the genus Symphysodon based on microsatellite markers: implications for systematics and classification

Manuella Villar Amado, Izeni P. Farias, and Tomas Hrbek

Received 21 December 2010; Accepted 2 May 2011

[Hsunami]

awww no pictures? LOL

[Rod]

Thanks for the link Paul. I found it an interesting read. :)

Its always fun watching the taxonomist contort a fixed name, for something that is inherently unfixed. All species are on the way to being something else....eventually. :D

[yogi]

Paul thanks for posting this. So the question is does it make discus classification clearer or fuzzier? Originally there were 4, then separate studies by Bleher and Kullander made only 3, now this new study shows 5. I know both Bleher and Kullander both only used mitochondrial DNA, where this new study uses nuclear DNA, but looks at a lot of previous work done by others. The two different DNA studies do look at differnt genetic codes. I know I'm recapping some of it, but it is a little hard to follow at times. They also took samples from locations that the others didn't look at. I also like the discus distribution map they posted in their study.

So this makes me think there are a lot of questions left to answer. How many wild strains are there? We know they can all interbreed, but are some of the hybrids from wilds really sterile? I guess time will only tell, but I do like a lot of the new wild color verities we are seeing from Hudson, Hans, Oliver and Snook.

[pcsb23]

So the question is does it make discus classification clearer or fuzzier? Good question, as things stand somewhere between 3 & 5!! Seriously though the paper suggests there are now 5.


...
Its always fun watching the taxonomist contort a fixed name, for something that is inherently unfixed. All species are on the way to being something else....eventually.


Originally there were 4, then separate studies by Bleher and Kullander made only 3, now this new study shows 5. I know both Bleher and Kullander both only used mitochondrial DNA, where this new study uses nuclear DNA, but looks at a lot of previous work done by others. The two different DNA studies do look at differnt genetic codes. As Rod says it is something of a contortion is it not? However if there are 5 clearly different sets of genes/DNA then ... but as Rod says it is something of a moving target I think.


I know I'm recapping some of it, but it is a little hard to follow at times. Only at times?? :bandana:


They also took samples from locations that the others didn't look at. I also like the discus distribution map they posted in their study. Certainly looks thorough, makes you wonder if there are any more to "discover" though ...

[Rod]

Hi Paul and Jerry,

People (and taxonomists) are natural essentialists, catergorizing in this case for the platonic discus. But evolution is such an anti-essentialist concept, it is not natural or easy for us to think of deviations from the platonic discus. For me personally, i still find the work of the taxonomist interesting and telling, but more for the reasons of the historical evolutionary path the 'species' has taken to arrive at the place it finds itself in, rather than some burning desire to have a name for it.

Rod:)

[Tigerfish]

Jerry,
I just emailed you a reply to your email to me with the link. I now notice the date, but not the journal, is in the starting post of this thread by pcsb23. The date and journal do not appear in the paper that came up from the link you sent me.
The paper by the same authors discussing speciation is also dated about the same time, same year. So some of my original reply doesn't apply.
I'll repeat it here as I emailed it to you without correcting....

Jerry,

Thanks. What's missing is the date. It does not appear to be the latest paper. Some of these same people have done more before and since. Others have also done DNA studies in the past three or four years and I need to put them all in date order.

This paper from which you sent my the link from Simply, has not been published in a journal. It could be part of another paper, incomplete, trashed, a draft copy, for internal use or whatever. I can't find it, and published papers are easy to find .

From quickly reading this paper, I can't see where there are five "species" of discus claimed. I only see five phenotypes were examined. That's a lot different than species. It only means five different looking fish or groups of fish. Actually they mention six groups elsewhere in the paper, but again, not as species. I'll have to go back to it and see what that was about.

This is not the latest paper on the subject it appears, by the same authors and others as well. It also addresses the matter in a different manner than simply determining speciation. This "paper" looks like notes incorporated in other papers that were published.


In the paper that they do discuss speciation (as I remember it - and it's not this one)...there is one species of discus with the Western green population showing more divergence to the others (non-"greens") than the others show to each other. So at this point in time there is one species of discus with the green discus perhaps a subspecies.

However the authors acknowledge that discus morphs intergrade, resulting in intermediate morphs and that some may be on the way to speciation. However, this can suddenly reverse itself...or not...in some/all places or not. We can't predict what will happen geologically, and environmentally. At this point in time there is one species. However there are some undescribed populations outside of Brazil where the authors worked that aren't considered in any of the papers.

As I've told you, there is really not a genetic heckel and hobbyists don't know what a heckel is. That can also be determined by breeding them which we've both done. The heckel phenotype is recessive and environmentally at effect so people who have possibly bred them either didn't get heckels or didn't even realize it.

The authors have also determined that much of the variation in appearance (phenotype) is environmental, which I've also been telling you. You can "create" phenotypes by manipulating the environment. This includes the heckel.

I got the paper a few moments ago. It's late, almost , one AM but from what I see their conclusion is one species with some qualification which I'll explain after I digest it all.

The are other more recent papers that may or may not refute anything earlier. They appear to address the molecular aspects of the study more as to technique, logic in making conclusions, etc. than speciation of discus per se. I've got a pile to go over to see which end is up...and again the Simply link shows no date. Maybe I'll call the author.

I can post this on Simply as well...but with now four to six papers..or more to read on the subject, I may need a day or two to sort it out as to conclusion in case I don't have it totally right above.


Marc