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Maintenance of clonal diversity during a spring bloom of the centric diatom Ditylum brightwellii.

Abstract

Maintenance of genetic diversity in eukaryotic microbes reflects a synergism between reproductive mode (asexual vs. sexual) and environmental conditions. We determined clonal diversity in field samples of the planktonic marine diatom, Ditylum brightwellii, during a bloom, when cell number increased by seven-fold because of rapid asexual division. The genotypes at three microsatellite loci were determined for 607 individual cell lines isolated during the 11 days of sampling. Genetic diversity remained high during the bloom and 87% of the cells sampled each day were genetically distinct. Sixty-nine clonal lineages were sampled two or more times during the bloom, and two clones were sampled seven times. Based on the frequency of resampled clonal lineages, capture-recapture statistics were used to determine that at least 2400 genetically distinct clonal lineages comprised the bloom population. No significant differences in microsatellite allele frequencies were observed among daily samples indicating that the bloom was comprised of a single population. No sexual stages were observed, although linkage equilibrium at two loci, high levels of allelic and genotypic diversity, and heterozygote deficiencies were all indicative of past sexual reproduction events. At the height of the bloom, a windstorm diluted cell numbers by 51% and coincided with a change in the frequency distribution of some resampled lineages. The extensive clonal diversity generated through past sexual reproduction events coupled with frequent environmental changes appear to prevent individual clonal lineages from becoming numerically dominant, maintaining genetic diversity and the adaptive potential of the population.

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  • Authors

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    Source

    Molecular ecology 14:6 2005 May pg 1631-40

    MeSH

    Diatoms
    Environment
    Eutrophication
    Gene Frequency
    Genetic Variation
    Genotype
    Linkage Disequilibrium
    Microsatellite Repeats
    Reproduction, Asexual
    Seasons
    Washington

    Pub Type(s)

    Comparative Study
    Journal Article
    Research Support, U.S. Gov't, Non-P.H.S.

    Language

    eng

    PubMed ID

    15836638