MEPS 273:163-172 (2004)  -  doi:10.3354/meps273163

ABSTRACT: Dispersal ability is key to the spreading of exotic species to new areas. Herein, we focus on the expansion processes along the French Atlantic coast of an exotic marine gastropod, Ocinebrellus inornatus, first detected in the Marennes-Oléron bay in 1995. Unlike many aquatic invaders, O. inornatus lacks a swimming larval stage. This feature may reduce its ability to expand within the area of introduction unless counterbalanced by human-mediated spreading. By analyzing the genetic diversity at 7 allozyme markers, we compared the genetic diversity and structure of 9 French, 3 American and 5 Asian (native) populations. The genetic differentiation between populations within each area was low and of similar magnitude. However, a genetic isolation by coastline distances was detected in Asia only. We draw 2 main conclusions from these results. First, the settlement of new populations along the French Atlantic coast is not associated with drastic founder events. Second, expansion along the French coast is enhanced by oyster-farming activities.

KEY WORDS: Colonization · Introduced species · Direct-developing species · Population genetics · Allozyme markers · Ocinebrellus inornatus