Andrew asks:
 
>Date:    Tue, 20 Oct 1998 09:17:46 -0500
>From:    "Andrew K. Rindsberg" <[log in to unmask]>
>Subject: Re: DNA question
>
>My question has to do with the results. Suppose that Art has his black box
>that rapidly and inexpensively sequences DNA. He finds that some snails
>look almost alike but have very different DNA. Very well, DNA is the code
>of life itself, so obviously these are different taxa
>(species/genera/etc.), and he is inspired to search for the morphologic
>details that might distinguish them in the field. More work is needed, but
>no change in principles.
>
>Then Art tests two snails that look very different but have almost
>identical DNA. He tests many more snails and finds that these results are
>consistent, not due to a mistake or to a single pathological individual. My
>questions for Michael Reagin and other interested conchologists are: Are
>these also separate taxa? Would the DNA specialist prefer to call them
>different subspecies rather than different species or genera? Is the DNA
>criterion the only one to be considered, or is morphology still considered
>to be a valuable tool in taxonomy?
>
>And what is a paleontologist supposed to do about it? Fossils usually don't
>retain soft parts, much less DNA.
>
 
Molecular data is but one tool that a systematist uses to test a
phylogenetic hypothesis concerning species relationships.  Some may argue
that it is a superior to morphology, behavior, etc. (Russ Minton, feel free
to chime in here buddy) but I believe it it just an additional piece of
data that should be used to elucidate relationships.  As for the
hypothetical question about two different looking animals being separate
taxa, that all depends on your species concept (evolutionary, phylogenetic,
etc).  Under the phylogenetic species concept one would probably consider
the different looking animals to be a single species based on the molecular
data.  Kevin Roe at U Alabama has the inverse problem here.  In looking at
the freshwater mussel, Potamilus inflatus (where if I have the story
correct) he has two very different populations at the molecular level but
thay are indistinguishable morphologically.  The molecular phylogenetisist
would probably call these seperate species (but it's really hard to write a
key based on differences in DNA!).   Shared common decent is the real
question here.  I would stay very far away from using subspecies and naming
these critters as such, as I don't believe we know exactly what a species
is  much less a subspecies.   As for you fossil people, it's one less tool
at your disposal.  Back to the stone age where you belong.
 
Kevin S. Cummings
Illinois Natural History Survey
607 E. Peabody Drive
Champaign, IL 61820
[log in to unmask]
http://www.inhs.uiuc.edu/cbd/collections/mollusk.html