| 1. |
- Ellegaard, M., et al.
(author)
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The species concept in a marine diatom: LSU rDNA-based phylogenetic differentiation in Skeletonema marinoi/dohrnii (Bacillariophyceae) is not reflected in morphology
- 2008
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In: Phycologia. - : Informa UK Limited. - 0031-8884. ; 47:2, s. 156-167
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Journal article (peer-reviewed)abstract
- The ubiquitous marine diatom genus Skeletonema includes several newly described species. This paper presents a study of morphology and LSU sequence diversity of one of these new species, Skeletonema marinoi. The 15 monoclonal strains (from the Swedish west coast, the Swedish east coast, Portugal and Canada) included in the study showed differences in LSU rDNA sequence within the morphospecies, with differences seen even among clones established from a single plankton net sample. Morphologically, all clones were indistinguishable from each other and from the closely related species Skeletonema dohrnii. In the original description of these two species, they were differentiated by the structure of the girdle bands. However, the girdle band types of both species were found within single samples of almost all clones of S. marinoi in this study. The LSU-based phylogeny is consistent with the split into two species, and there may be a difference in their bioaeoszraphical distribution. We therefore do not at present suggest that the two species be merged. Questions regarding species delimitation and cryptic species within protists often arise from such studies that include data from both morphological and DNA sequence analysis, and such questions are addressed here.
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| 2. |
- Godhe, Anna, 1967, et al.
(author)
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Linking the planktonic and benthic habitat: genetic structure of the marine diatom Skeletonema marinoi
- 2010
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In: Molecular Ecology. - 0962-1083. ; 19:20, s. 4478-4490
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Journal article (peer-reviewed)abstract
- Dormant life stages are important strategies for many aquatic organisms. The formation of resting stages will provide a refuge from unfavourable conditions in the water column, and their successive accumulation in the benthos will constitute a genetic reservoir for future planktonic populations. We have determined the genetic structure of a common bloom-forming diatom, Skeletonema marinoi, in the sediment and the plankton during spring, summer and autumn two subsequent years (2007-2009) in Gullmar Fjord on the Swedish west coast. Eight polymorphic microsatellite loci were used to assess the level of genetic differentiation and the respective gene diversity of the two different habitats. We also determined the degree of genetic differentiation between the seed banks inside the fjord and the open sea. The results indicate that Gullmar Fjord has one dominant endogenous population of S. marinoi, which is genetically differentiated from the open sea population. The fjord population is encountered in the plankton and in the sediment. Shifts from the dominant population can happen, and in our study, two genetically differentiated plankton populations, displaying reduced genetic diversity, occurred in September 2007 and 2008. Based on our results, we suggest that sill fjords maintain local long-lived and well-adapted protist populations, which continuously shift between the planktonic and benthic habitats. Intermittently, short-lived and mainly asexually reproducing populations can replace the dominant population in the water column, without influencing the genetic structure of the benthic seed bank.
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