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
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.
- Churro CI, Carvalho CC, Rodrigues F, Craveiro SC, Calado AJ, Casteleyn G, Lundholm N (2009) Diversity and abundance of potentially toxic Pseudo-nitzschia Peragallo in Aveiro coastal lagoon, Portugal and description of a new variety, P. pungens var. aveirensis var. nov. Diatom Res (in press)Google Scholar
- Goudet J (2001) fstat, a program to estimate and test gene diversities and fixation indices (version 2.9.3). Available from http://www2.unil.ch/popgen/softwares/fstat.htm
- Heip C (1989) The ecology of the estuaries of Rhine, Meuse and Scheldt in the Netherlands. In: Ross JD (eds) Topics in marine biology: proceedings of the 22nd European marine biology symposium, Barcelona. Sci Mar 53:457–463Google Scholar
- Hellberg ME, Burton RS, Neigel JE, Palumbi SR (2002) Genetic assessment of connectivity among marine populations. Bull Mar Sci 70:273–290Google Scholar
- Lee AJ (1980) North Sea: physical oceanography. In: Banner FT, Collins MB, Massie KS (eds) The North-West European shelf sea: the seabed and the sea in motion. II. Physical and chemical oceanography, and physical resources. Elsevier, Amsterdam, pp 467–493Google Scholar
- Nagai S, Lian C, Yamaguchi S, Hamaguchi M, Matsuyama Y, Itakura S, Shimada H, Kaga S, Yamauchi H, Sonda Y, Nishikawa T, Kim CH, Hogetsu T (2007) Microsatellite markers reveal population genetic structure of the toxic dinoflagellate Alexandrium tamarense (Dinophyceae) in Japanese coastal waters. J Phycol 43:43–54CrossRefGoogle Scholar
- Park SDE (2001) Trypanotolerance in West African cattle and the population genetic effects of selection. Ph.D. thesis, University of DublinGoogle Scholar
- Pritchard JK, Wen X, Falush D (2007) Documentation for structure software: Version 2.2. Available from http://pritch.bsd.uchicago.edu/structure.html
- Valiere N (2002) gimlet: a computer program for analysing genetic individual identification data. Mol Ecol Notes 2:377–379Google Scholar
- Weir BS, Cockerham CC (1984) Estimating F-statistics for the analysis of population structure. Evolution 38:1358–1370Google Scholar