Two locations in the Western Scheldt were sampled for four age classes of the burrowing bivalveLimecola balthica (Linnaeus, 1758). The aim of the research was to determine whether sandnourishments and subsequent bivalve mortality may be expected to lead to extirpation orreplenishment from nearby sources. The study locations were rich subtidal bivalve beds near 'DeKapellenbank' and 'De Suikerplaat'. The samples were examined for five genetic loci (microsatellites)and for the morphological character shell globosity. No genetic structure was observed, neitherbetween the locations, nor among age groups or in some other, not previously defined way. Shellshape was found to show small statistical differences between locations. However, the distribution ofthe shape data was not uniform and therefore the biological relevance of these small potentialdifferences cannot be stated. We conclude that genetic connectivity between the two locations isstrong. This implies that, at evolutionary time scales, sufficient gene flow between the locations hasoccurred to maintain genetic and morphological similarity. The two locations may be connected byrecruitment directly or indirectly. It is, however, possible that on ecological time scales gene flow isreduced or even absent ('Waples effect'). On the basis of these data there is no reason to assumethat one location will not be recolonised from the other in case the population would be removed,e.g. because of dredging activities. The data cannot predict the time scale of recolonisation, whichmay theoretically be anything from years to millennia. |
