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Maintenance of genetic diversity in heterosigma akashiwo by temporal variability in its environment
Author(s) -
Lakeman M.B.,
Cattolico R.A.
Publication year - 2003
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.2003.03906001_91.x
Subject(s) - biology , heterosigma akashiwo , genetic diversity , locus (genetics) , evolutionary biology , nucleotide diversity , genetic variation , haplotype , genetics , population , genotype , ecology , algal bloom , gene , nutrient , phytoplankton , demography , sociology
Heterosigma akashiwo (Hada) Hada ex Y. Hara et Chihara (Chromophyta: Raphidophyceae) is a coastal HAB forming species that is not known to undergo sexual reproduction. Ribosomal ITS sequences for 36 strains of Heterosigma have been determined and found to be identical except for two strains that had one single nucleotide polymorphism each. Despite the apparent absence of meiosis and the ostensible homogeneity of genotypes (at least at the ITS locus), different strains of Heterosigma display a very wide range of phenotypes. This inconsistency suggests that greater genetic diversity exists in Heterosigma than is evident through sequence analysis of the ITS region. Data will be presented summarizing efforts to develop better genetic markers for examining intrapopulational diversity. Results of experiments examining the effects of nutrient concentration in batch culture on growth response have demonstrated that sufficient haplotype variability exists in established culture strains to allow Darwinian selection, even when these strains are “clonal”. We propose that batch culture imposes a sequence of different selection pressures on a rapidly dividing population of cells, and this environmental variation promotes the maintenance of genetic diversity. Extrapolating the batch culture scenario to the much more highly dynamic marine coastal environment, it becomes apparent that the observed phenotypic variation between Heterosigma strains is largely a function of a diverse haplotype distribution, maintained, in a large part, by patchy resource availability on both temporal and spatial scales.