Hi Linda
About 6 years ago when I was working with a researcher from San Francisco State
Univ - Conservation Genetics Lab. Calliostoma parsimony analysis via molecular
CO1 study.  We discussed some research that had been recently completed on the
M. radix - nigritis complex.

The findings were interesting:
Generically speaking they are all one species.  Populations were systematically
sampled all down the west American coasts and their DNA analyzed.  From
population to population there was no significant difference in the DNA from
one population to the next.  However, when you make large jumps, say from mid-
California to Baja, there was enough difference to possibly conclude they could
be differnt species.  There is no dividing line between one species to the
next, just a slow minor but progressive change in the gene pool from one colony
to the next.

In short, it points out the relativity of even using molecular study to
determine speciation.  As we all know shells tend to be extremely variable, and
things such as temperature, food sources, and trace elements can be a big
factor in a shells looks, and population isolation repeats characteristics
differentiating one colony from another.  ...Even though the guy in the cubicle
next to you may seem like another species... he is still the species Homo
sapien.

Unfortunately I do not know what the citation is for this study, it was
probably someone's doctoral dissertation.  I have not spoken with, or been able
to find the researcher in many years, so even the work he was doing for me I
can not attain.

As for me I do not have a problem with names on distinct forms.  That is the
beauty and essence of Shell Collecting.... and the systematicist will continue
to change names, create new name, synonymize them, and restore them again until
eternity.  So have fun and enjoy the shells!!!

Best Regards,
Leslie Allen Crnkovic

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Hello, CONCH-Lers!
I think I know why my confusion.  Instead of having mixed up the localities, I
apparently have nigritis and ambiguus, not nigritis and radix.  I failed to
consider ambiguus as a possibility for the one species.
Thanks,
Linda
P.S.  Now all I have to get is a specimen of Radix, so that I have the three
species to examine (assuming that ambiguus has specific status).