Ross, Jim,
It is a very good question.  The barriers to species with planktonic larvae may include distance (depending on how long they can stay in the plankton without settling down), water temperature, appropriate bottom conditions upon arrival and current patterns.  Species like Turbinella angulata, which has crawl away larvae and apparently cannot cross bathyl depths, are more difficult to disperse.  It is a not uncommon early to late Pleistocene fossil in Florida and may have crossed over the Florida Straits from (to?) the Bahamas during a very low water period corresponding to intense glaciation.  It may have come via the Yucatan, which seems to have a good connection with Florida via the Keys, again, perhaps, at low water times.  What the connection is between the Yucatan and the Bahamas is less clear.
Allen Aigen
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From: Jim Miller <[log in to unmask]>
To: [log in to unmask]
Subject: Re: Amphi-Atlantic species
Date: Thu, 14 Nov 2002 22:56:45 -0500

>I guess the real question is why are there not more non-boreal species
>that occur on both sides of the Atlantic?

Ross,

The question that has me baffled is how there are certain very common
shells found in Florida (Busycon species, for instance) that are not found
in the Bahamas -- just 54 miles east. Conversely, Turbinella angulata,
which is a prolific species in the Bahamas, is not found in Florida. While
I have found many Cypraea zebra in the Bahamas, I have never seen a
C. cervus. Has anyone else collected this species in Bahamian waters?

Best regards from chilly (for us) Florida,
Jim

--



Allen Aigen
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