>Gary, are there the same intergrading habitats and corresponding shell forms in
>the Gloripallium as with Turbo cornutus?
 
From examination of shells labelled as Gloripallium pallium and G. speciosum
in our collection (all of them identified as G. pallium by Tom Waller in
1977), I find that there are some specimens that seem to intergrade.
However, I'm not familiar with exactly what features are cited as separating
them. I don't know if habitats intergrade.
 
>It gives the APPEARANCE of a lack of
>continuity in how species are determined.  How can he say these two similar
>shells are different, but, on the other hand, these two vastly different shells
>are one in the same?  I don't even know what the criteria are.
 
The criteria are consistent morphological (including anatomical) difference,
whether large or small, so long as the differences are genetically based,
and consistent genetic difference. Differences in habitat and geography are
not good criteria for saying that two entities either are or are not
separate species. Differences in habitat or geography, however, often spur
deeper investigation into morphology and genetics. In some cases species can
have very small differences that are consistent, in others a single species
can have huge variation, but the presence of intergrades prevents one from
splitting it into more than one species.
 
I've seen cases where one had to examine literally thousands of specimens to
arrive at an understanding of the species and its range of variation. For
other species, seeing a few specimens is good enough.  Unfortunately,
there's no way to know in advance how many specimens you need to see.
 
Gary
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Gary Rosenberg, Ph.D.                     [log in to unmask]
Malacology & Invertebrate Paleontology    gopher://erato.acnatsci.org
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