Lack of population genetic structuring in the marine planktonic diatom Pseudo-nitzschia pungens (Bacillariophyceae) in a heterogeneous area in the Southern Bight of the North Sea
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Several marine holoplanktonic organisms show a high degree of geographically structured diversity for which it often remains unclear to what extent this differentiation is due to the presence of cryptic taxa. For the genetically distinct diatom Pseudo-nitzschia pungens var. pungens, we used six microsatellite markers to investigate the spatial and temporal genetic composition in the heterogeneous Southern Bight of the North Sea. Although our sampling area (ca. 100 km) comprised water bodies with different environmental conditions (marine, estuary, saline lake) and different degrees of connectivity (from complete isolation to supposedly free exchange between environments), no evidence of genetic differentiation was found. Expanding our sampling area (ca. 650 km), suggested a homogenous population structure over even larger areas in the North Sea. Our results suggest that the population structure of this diatom is mainly shaped by strong homogenizing effects of gene flow preventing genetic drift, even in water bodies with limited connectivity.
KeywordsInternal Transcribe Spacer Water Residence Time Nuclear Microsatellite Locus German Part Storm Surge Barrier
Financial support for this research was provided by the Research Programmes G.0292.00 and G.0197.05 of the Flemish Fund for Scientific Research (FWO) and the BOF-project GOA 12050398 of Ghent University. G.C. is funded by the Flemish Institute for the Promotion of Innovation by Science and Technology (IWT). T.B. was supported by FWO-grant G.0404.07. We thank the crew of the Zeeleeuw (VLIZ, Flemish Marine Institute) for the sampling in the North Sea and Frederik Leliaert for help with sampling in the Westerschelde, Oosterschelde and Lake Grevelingen. Andy Vierstraete is thanked for allele fragment electrophoresis.
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