title: Implications of life-history transitions on the population genetic structure of the toxigenic marine dinoflagellate Alexandrium tamarense.
abstract: Genotypic or phenotypic markers for characterization of natural populations of marine microalgae have typically addressed questions regarding differentiation among populations, usually with reference to a single or few clonal isolates. Based upon a large number of contemporaneous isolates from the same geographical population of the toxigenic species Alexandrium tamarense from the North Sea, we uncovered significant genetic substructure and low but significant multilocus linkage disequilibrium (LD) within the planktonic population. Between the alternative molecular genotyping approaches, only amplified fragment length polymorphism (AFLP) revealed cryptic genetic population substructure by Bayesian clustering, whereas microsatellite markers failed to yield concordant patterns. Both markers, however, gave evidence for genetic differentiation of population subgroups as defined by AFLP. A considerable portion of multilocus LD could be attributed to population subdivision. The remaining LD within population subgroups is interpreted as an indicator of frequency shifts of clonal lineages during vegetative growth of planktonic populations. Phenotypic characters such as cellular content and composition of neurotoxins associated with paralytic shellfish poisoning (PSP) and allelochemical properties may contribute to intra- or inter-annual differentiation of planktonic populations, if clonal lineages that express these characters are selectively favoured. Nevertheless, significant phenotypic differentiation for these characters among the genetically differentiated subgroups was only detected for PSP toxin content in two of the four population subgroups. By integrating the analysis of phenotypic and genotypic characteristics, we developed a conceptual population genetic model to explain the importance of life-cycle dynamics and transitions in the evolutionary ecology of these dinoflagellates.
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany. talpermann@meeresforschung.de
authors.forename: Tilman J
authors.initials: TJ
authors.lastname: Alpermann
authors.forename: Bánk
authors.initials: B
authors.lastname: Beszteri
authors.forename: Uwe
authors.initials: U
authors.lastname: John
authors.forename: Urban
authors.initials: U
authors.lastname: Tillmann
authors.forename: Allan D
authors.initials: AD
authors.lastname: Cembella
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D000818:Animals; D004141:Dinoflagellida / Q000235:genetics*; D005819:Genetic Markers; D005828:Genetics, Population; D005838:Genotype; D015810:Linkage Disequilibrium; D008387:Marine Toxins / Q000235:genetics; D018895:Microsatellite Repeats; D010641:Phenotype; D012098:Reproduction; D017422:Sequence Analysis, DNA
chemical_list: D005819:Genetic Markers; D008387:Marine Toxins