Two questions:

I read that A) Littorina littorea lives on rocks, B) that it is moving
southwards in recent times (last 150 years), and C) that it may or may not
change rocky habitats.

Q1: Isn't it able to spread to the south only in recent times ONLY because
earlier rocky environments are all man made and used to be absent on the
eastcoast between Maine and Florida?
Q2: if all rocky environment is man-made and to some degree "artificial"
then is it not likely that L. littorea has a noticeable but totally harmless
impact on its habitat until it reaches an equilibrium with other organisms
(as in northwestern Europe, and Canada)?

The question, how far south will it reach perhaps can be answered by looking
at the situation in Europe. There are a few reports of failed settlement in
the Mediterranean and Canary Islands (temperature of the seawater during the
summer (well) above 21 degrees Celsius (70 Fahrenheit), and on the shore
even higher. That might be the upper limit (in temperature) and lower limit
(in latitude). I think this more or less correponds with Cape Hatteras.

Marien
www.mollus.nl



----- Original Message -----
From: "ross mayhew" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, December 13, 2004 6:20 AM
Subject: Re: molluscs invading North America: what about Littorina littorea?


> Thanks a lot to all who have replied on this topic - i've learned a
> lot!    That said, the question regarding exactly what changes the
> invasion of New England by this prolific and fairly selective herbivore
> has caused, with regards to inter and sub-tidal ecosystems?  The
> suggestion has been made that they denuded much of the rockier parts of
> the coastline has been made, but this seems illogical to me, since there
> are plenty of habitats which have good densities of L. littorea, AND a
> reasonable covering of algae at the same time.  Are there any localities
> where we have good "before" and "after" descriptions of habitats invaded
> by this species?
>
> From wet and windy old New Scotland,
> Ross Mayhew.
>
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