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Re: List of ID corrections was Ap. jurua


I agree, DNA studies are not 'the be all to end all' for answering all species
related questions. DNA research is just one of many resources that we can use to
determine how closely or remotely related one organism is to another. It's true
that every specimen within a species has slightly different DNA - but in sexual
organisms all should have the same mitochondrial DNA sequence passed down from
their mother. The more this mitochondrial sequence differs in closely related
forms, the more likely that they are very different biological entities or species
(whatever 'species' means).

The neon tetras example doesn't exactly apply here. We all recognize that they are
sufficiently different to be considered different species. I can imagine that the
genetics people could negate the phylogenists' ideas by claiming that we are merely
seeing evolutionary convergence of species from different lineages adapting to
similar environments. Who is to say who is correct? I think, for example, that the
Rummynose/Red-nose tetras are still listed in 2 genera (Petitella & Hemmigrammus ).
Are they closely related or do they show convergence? The caetei example uses 2
forms that are virtually identical, but still show more divergence than between
different looking fish from different genera.

The question I am raising is: is it acceptable to cross 2 similar appearing, but
genetically divergent, forms while we wouldn't cross 2 different looking, but
genetically more closely related, forms? My opinion is no. Others may think
otherwise. This just shows that we really don't understand what separates
populations. Species, after all, are artificial. They are man made, used to
organize the world around us.

Mike Wise

Randy Carey wrote:

> I highly suspect DNA studies.  I remember reading an old TFH issue where
> the researcher examined the DNA of the neon, cardinal, and green neon
> tetras -- he concluded that they are not closely related.  Then Weitzman
> did a phylogenetic study in which he examined and compared physical traits.
> His study provided clear evidence to what we intuitively observe -- that
> the three are closely related to each other and far more closely than to
> any other species.
> The problem seems to be that we do not know yet how to draw good
> conclusions from DNA regarding species relationships.  Two siblings (human
> or otherwise) will have different DNA.  So if DNA varies that much, how
> reliable is it for species-to-species comparisons?!
> So I favor phylogenetic study of species-consistent features rather than
> today's genetic study.
> I can see how, from the perspective of your studies, that you feel
> splitting is safer.  But from a different perspective, I feel that lumping
> is safer.... If I get an apisto and I don't know the collection data, I
> must rely upon the features to help me identify it.  Usually I can do a
> pretty good job mapping the fish to one in "the books."  And if two or
> three of the newer populations are not visually distinguishable (to the
> hobbyist), then I feel it is "safer" to label it with the more standard
> name instead of trying to pick one of the "population" names.  As long as
> I'm honest with myself and with buyers that I'm a lumper, going with the
> "lumped" name is safer and more apt to be correct.  If I must find the
> precise match with some location name, then I'm apt to be frustrated and
> far too often uncertain.
> So if I have a reliable location (or new form) name, I'll keep
> it.  Otherwise I'm quite content with a "lumped" name -- an identification
> that other knowledgeable aquarists can agree with -- and should reach on
> their own study.  I know that this is not the purist approach that an
> ichthyologist will take -- but, gee, I'm an aquarist, not a scientist.  If
> it has all the features of a eunotus, and it behaves like a eunotus, then
> how can one expect more from an aquarist than to call it a eunotus?  And if
> there is some very subtle or internal difference that is not observable,
> how does that difference affect the aquarist?
> --Randy  ( the lumper ;-)
> At 10:09 AM 5/13/2002, Mike wrote:
> >Right now I prefer to play it safe & split as much as
> >possible. As I've said before, if you split & keep 'forms' true, then you can
> >always cross them when you find that 2 forms are the same species. If you
> >cross
> >2 forms and then discover that they are different species, there's a
> >chance that
> >you will lose 1 or both pure species in the hobby.
> >
> >So the question now is whether it is better to be a lumper or a splitter.
> >Ongoing DNA studies are pointing to the probability that there are more
> >distinct
> >species than mere geographic populations of apistos. DNA studies have already
> >shown that the genetic difference between A. caetei from the type locality
> >(Rio
> >Caeté) and A. cf. caetei (Guamá) from the Rio Guamá are greater than the
> >difference in mitochondria between all species of Mbuna in Lake Malawi - and
> >this includes species in different genera!  This is very disturbing to me
> >because these 2 forms are found in neighboring streams within a few miles of
> >each other. These 2 caetei-complex fish that are virtually identical when
> >preserved. The type form of A. caetei is somewhat more colorful than the Guamá
> >form when alive. Are these 2 forms distinct species? If we say they are
> >the same
> >species, then do we lump all Malawi Mbuna into a single species?
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This is the apistogramma mailing list, apisto@listbox.com.
For instructions on how to subscribe or unsubscribe or get help,
email apisto-request@listbox.com. apisto-digest@listbox.com also available.
Web archives at http://lists.thekrib.com/apisto