Dear Harry

It is indeed true that Cepaea hortensis is a pre-Viking native of
Newfoundland and eastern Canada.

The proof of this fact is that reliable carbon dates, that considerably
pre-date the Viking era, exist for Cepaea hortensis collections (both
paleontological and archaeological) from our region.

However, the possibility that a number of post-Viking introductions of
Cepaea hortensis may now be layered upon the original North American
populations should not be ruled out. I would be surprised if such were NOT
the case.

... I MUST NOW COMMENT on the rather dated quote attributed to Andrew
Grebneff: "According to John Maunder (Newfoundland Museum, St. Johns) and
Ron Noseworthy, not all of Newfoundland was glaciated during the
Pleistocene/Holocene, and the colonies there survived" ...

Current scientific thinking no longer substantially support this idea ...

To be sure, a few high cliff faces in our western mountains may have
remained above the glacial ice, and thus may have provided a few small
precarious refugia for some small invertebrates (perhaps including some
small molluscs? - the endemic Vallonia terranovae, which is found only in
that region, MAY be a possible candidate?). However, even the tops of
Newfoundland's Long Range Mountains (a northern extension of the Appalachian
Mountain chain), long thought to have been ice-free even during major
glacial events, have now been convincingly shown, using isotopic techniques,
to have been well covered with non-flowing "cold-based" ice during those times.

The more likely "refugial scenario" for the Newfoundland area seems to
involve the "off-shore fishing banks", to the south of the Island of
Newfoundland, which were clearly exposed above sea-level, and supposedly at
least partially ice-free, during glacial times, when world sea-levels were
known to have been more than 100 metres lower.

Nonetheless, I should stress that the majority of modern-day glacial
geologists seem to be of the opinion that these fishing banks, even
including our very extensive Grand Bank, were almost entirely (although not
necessarily completely) glaciated.

Biologists, on the other hand, continue to come up with any number of
reasons why these same fishing banks must have been at least substantially
unglaciated. Perhaps the truth lies somewhere in between. In the meantime,
the debate is FAR from being resolved.

... The land-bridge theory, however, can be safely debunked. There is no
modern evidence for it!

John Maunder

----- Original Message -----
From: Harry G. Lee
To: [log in to unmask]
Sent: Friday, November 27, 2009 3:09 PM
Subject: Re: [CONCH-L] Grove snails Kentucky

Dear Erick,

Pilsbry (1939: 8) discussed the North American populations of Cepaea
nemoralis (Linnaeus, 1758) at some length. That it originated in Europe is a
near certainty based on its taxonomic affinities.

Winkley (1904) seems to have made the first suggestion of its preglacial
occurrence on this side of the Atlantic. Citing the peculiar distribution on
many uninhabited islands poorly suited for maritime exploitation along the
northeast American coast, he immediately dismissed transport by Norsemen and
other Precolonial visitors. That Pleistocene glaciation covered much of the
species' range in New England is indisputable, but these islands and some
mainland glacier-free areas, e.g., Cape Ann and Cape Cod, MA could well have
served as refugia. Further, Andrew Grebneff posted a comment to this forum a
while back: "According to John Maunder (Newfoundland Museum, St. Johns) and
Ron Noseworthy, not all of Newfoundland was glaciated during the
Pleistocene/Holocene, and the colonies there survived." Pleistocene fossils
and Precolumbian archaeological occurrences further bolster this argument.

How did it get here? One theory has it that there was late Tertiary and
Pleistocene uplift of the Arctic lands and a land bridge existed from
Scotland to Iceland to Greenland to Labrador. Such a connection might also
explain the European-Eastern North American distribution of other
landsnails, e.g., Zoogenetes harpa, certain Euconulus spp., Pupilla
muscorum, certain Vallonia spp., etc.

Thus, not all snail taxa originating in Europe reached and became
established in eastern North America through human agency. Most maybe, but
not all.

On the other hand, several eastern North American snails have been
introduced into Europe, but that's another story and not one involving Cepaea.

Harry

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