I've enjoyed this thread on Smaragdia, especially since I finally got to collect my own specimens in the Florida Keys last December.

As a paleontologist I see no problem with the possibility of separate species in 5 my, especially since we already have what are considered cognate species of mollusks (conchs, murex, etc) on either side of the Central America landbridge that formed between 3 and 4 million years ago.

But I am a bit dubious about the "biological definition of a species" in light of recent records of hybrids between closely related species (even the so-called "Darwin's finches") interbreeding to produce viable offspring that could in turn become new species.  Maybe that's how we got Lambis arachnoides (aka L. wheelwrighti)?

Rick Batt
North Tonawanda, NY

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Is the door then still open just a crack for the possibility of two species separated by 5 million years?

When I was a kid, the answer could have been determined by simply dropping specimens from the respective populations in an aquarium and seeing if they breed. That definition wouldn't pass muster any more, I guess.

David Kirsh
Durham, NC

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