1. ¹Katholieke Universiteit Leuven, Laboratory of Aquatic Ecology, Ch. de Bériotstraat 32, Leuven 3000, Belgium
2. ²Marine Research Institute Reykjavík, Division of Population Genetics, C/O Biotechnology House, Keldnaholt, Reykjavík IS-112, Iceland
3. ³School of Biology, Georgia Institute of Technology, 310 Ferst Drive, Atlanta, GA 30332, USA

Correspondence: C Pampoulie, Division of Population Genetics, Marine Research Institute, C/O Biotechnology House, Keldnaholt, IS-112 Reykjavik, Iceland. E-mail address: chrisp@iti.is

Received 28 October 2002; Accepted 9 September 2003; Published online 3 March 2004.

Abstract

Marine fish seem to experience evolutionary processes that are expected to produce genetically homogeneous populations. We have assessed genetic diversity and differentiation in 15 samples of the sand goby Pomatoschistus minutus (Pallas, 1770) (Gobiidae, Teleostei) from four major habitats within the Southern Bight of the North Sea, using seven microsatellite and 13 allozyme loci. Despite its high dispersal potential, microsatellite loci revealed a moderate level of differentiation (overall F_ST=0.026; overall R_ST=0.058). Both hierarchical analysis of molecular variance and multivariate analysis revealed significant differentiation (P<0.01) between estuarine, coastal and marine samples with microsatellites, but not with allozymes. Comparison among the different estimators of differentiation (F_ST and R_ST) pointed to possible historical events and contemporary habitat fragmentation. Samples were assigned to two breeding units in the estuary and coastal region. Despite this classification, there were indications of a complex and dynamic spatiotemporal structure, which is, most likely, determined by historical events and local oceanic currents.