Hello Erick et al

re L. obtusata: the shells featured  by Marlo for  were a  selection
on his part from a larger lot of shells  that I collected locally at a
single location. Within that population, and across different
localities, I will see a considerable variation in shell shape,
including height, so overall I don't think you can read too much into
that vs. the European situation of obtusata vs. fabalis, where shell
morphology can differ between those two species (albeit with some
overlap).

To my knowledge, nobody has ever recorded fabalis from 'mainland'
North America; the Malacolog database notes records from Greenland,
and one dubious record from Canada that was not verified.  At the same
time, i don't know to what extent, if any, scientists have searched
with the specific intent of checking features such as penis size that
are used to separate the two species in Europe.

While  I have seen tall shells and flat shells, one thing I have never
seen in any American populations of obtusata is  the pattern of
spotting/freckles or whatever the term for it might be that I often
see on European shells of 1 or both species, for what that is worth.
All the shells I have seen are either solid color, or banded, but of
course others' experience may vary from mine.

On 11/20/21, Erick Staal <[log in to unmask]> wrote:
> Excellent photos. Thank you!
>
> One of the species is amphiatlantic (Littorina obtusata) and personally
> I know that species from mary places on the European Atlantic and North
> Sea coasts, and the shell morphology of the American specimens really
> looks different to me compared to the European ones (American specimens
> are much less flat than over here). Also: on the European side of the
> Atlantic L.obtusata forms a species complex with L.fabalis. Thus I'm
> wondering if the American L.obtusata are really that species or a
> distinct, but different, member of the species complex.
>
> See also e.g.:
>
> https://bmcecolevol.biomedcentral.com/articles/10.1186/s12862-019-1561-6
>
> Sincerely, Erick
>
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