Native or not? New research by a team of scientists has called into question the idea that the common periwinkle (Littorina littorea) has been living on the Atlantic Coast of North America for the past 8000 years. While previous genetic studies had concluded that this was the case, a new study says there is actually lots of genetic variation in North American populations that was not explained by the European snails that were sampled. Coupled with the fact that the two "winkle" shells (hey, that's what they call them in the UK) that supposedly dated back to the time of the Vikings have now gone missing, it now seems possible that later European introductions of the snail could have led to its spread along the coasts of the US and Canada. While one author of the previous study seems to have switched sides, this still a contentious issue...the Nature story alludes to a response by one of the dissenters but I can't find a link yet. Sounds like they need to do some more sampling!
You can read more about it at Nature's News site, or track down the full articles:
Chapman, J.W., Carlton, J.T., Bellinger, M.R. and Blakeslee, A.M.H. 2007. "Premature refutation of a human-mediated marine species introduction: the case history of the marine snail Littorina littorea in the Northwestern Atlantic." Biological Invasions.
Wares, J.P., Goldwater, D.S., Kong, B.Y., and Cunningham, C.W. "Refuting a controversial case of a human-mediated marine species introduction." 2002. Ecology Letters. 5: 577-584.