Molecular subdivision of the marine diatom Thalassiosira rotula in relation to geographic distribution, genome size, and physiology
Whittaker, Kerry A.
Rignanese, Dayna R.
Olson, Robert J.
Rynearson, Tatiana A.
MetadataShow full item record
Marine phytoplankton drift passively with currents, have high dispersal potentials and can be comprised of morphologically cryptic species. To examine molecular subdivision in the marine diatom Thalassiosira rotula, variations in rDNA sequence, genome size, and growth rate were examined among isolates collected from the Atlantic and Pacific Ocean basins. Analyses of rDNA included T. gravida because morphological studies have argued that T. rotula and T. gravida are conspecific. Culture collection isolates of T. gravida and T. rotula diverged by 7.0 ± 0.3% at the ITS1 and by 0.8 ± 0.03% at the 28S. Within T. rotula, field and culture collection isolates were subdivided into three lineages that diverged by 0.6 ± 0.3% at the ITS1 and 0% at the 28S. The predicted ITS1 secondary structure revealed no compensatory base pair changes among lineages. Differences in genome size were observed among isolates, but were not correlated with ITS1 lineages. Maximum acclimated growth rates of isolates revealed genotype by environment effects, but these were also not correlated with ITS1 lineages. In contrast, intra-individual variation in the multi-copy ITS1 revealed no evidence of recombination amongst lineages, and molecular clock estimates indicated that lineages diverged 0.68 Mya. The three lineages exhibited different geographic distributions and, with one exception, each field sample was dominated by a single lineage. The degree of inter- and intra-specific divergence between T. gravida and T. rotula suggests they should continue to be treated as separate species. The phylogenetic distinction of the three closely-related T. rotula lineages was unclear. On the one hand, the lineages showed no physiological differences, no consistent genome size differences and no significant changes in the ITS1 secondary structure, suggesting there are no barriers to interbreeding among lineages. In contrast, analysis of intra-individual variation in the multicopy ITS1 as well as molecular clock estimates of divergence suggest these lineages have not interbred for significant periods of time. Given the current data, these lineages should be considered a single species. Furthermore, these T. rotula lineages may be ecologically relevant, given their differential abundance over large spatial scales.
© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in BMC Evolutionary Biology 12 (2012): 209, doi:10.1186/1471-2148-12-209.
The following license files are associated with this item:
Showing items related by title, author, creator and subject.
McNichol, Jesse C. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-09)Chemoautotrophic ecosystems at deep-sea hydrothermal vents were discovered in 1977, but not until 1995 were free-living autotrophic Epsilonproteobacteria identified as important microbial community members. Because the ...
Distribution of hydrocarbons in a salt marsh ecosystem after an oil spill and physiological changes in marsh animals from the polluted environment Burns, Kathryn A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1975-06)The studies described in this thesis were designed to answer several problems relating to the recovery of a salt marsh heavily polluted by an accidental spill of Number 2 fuel oil. Field and laboratory studies were ...
Orchard, Elizabeth Duncan (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-02)Primary producers play a critical role in the oceanic food chain and the global cycling of carbon. The marine diazotroph Trichodesmium is a major contributor to both primary production and nitrogen fixation in the tropical ...