Genetic variation in the diatomFragilaria capucina (Fragilariaceae) along a latitudinal gradient across North America

Lewis, Raymond J.; Jensen, Susan I.; DeNicola, Dean M.; Miller, Virginia I.; Hoagland, Kyle D.; Ernst, Stephen G.

doi:10.1007/bf00982534

Cited by 40 publications

(29 citation statements)

References 32 publications

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“…Lundholm et al 2003;Montresor et al 2003), and Skeletonema (Gallagher 1982;Medlin et al 1991;Sarno et al 2005) show that apparently minor morphological differences may be significant, marking the boundaries between species. Surprising levels of genetic diversity have been demonstrated in a number of planktonic diatoms, both marine and freshwater (Lewis et al 1997;Mann 1999b;Rynearson & Armbrust 2000Evans et al 2005). In addition, the ease with which hitherto unknown species can be discovered (e.g.…”

Section: Speciation and Microevolutionmentioning

confidence: 99%

Evolution of the diatoms: insights from fossil, biological and molecular data

2006

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Molecular sequence analyses have yielded many important insights into diatom evolution, but there have been few attempts to relate these to the extensive fossil record of diatoms, probably because of unfamiliarity with the data available, which are scattered widely through the geological literature. We review the main features of molecular phylogenies and concentrate on the correspondence between these and the fossil record; we also review the evolution of major morphological, cytological and life cycle characteristics, and possible diatom origins. The first physical remains of diatoms are from the Jurassic, and well-preserved, diverse floras are available from the Lower Cretaceous. Though these are unequivocally identifiable as centric diatoms, none except a possible Stephanopyxis can be unequivocally linked to lineages of extant diatoms, although it is almost certain that members of the Coscinodiscophyceae (radial centrics) and Mediophyceae (polar centrics) were present; some display curious morphological features that hint at an unorthodox cell division mechanism and life cycle. It seems most likely that the earliest diatoms were marine, but recently discovered fossil deposits hint that episodes of terrestrial colonization may have occurred in the Mesozoic, though the main invasion of freshwaters appears to have been delayed until the Cenozoic. By the Upper Cretaceous, many lineages are present that can be convincingly related to extant diatom taxa. Pennate diatoms appear in the late Cretaceous and raphid diatoms in the Palaeocene, though molecular phylogenies imply that raphid diatoms did in fact evolve considerably earlier. Recent evidence shows that diatoms are substantially underclassified at the species level, with many semicryptic or cryptic species to be recognized; however, there is little prospect of being able to discriminate between such taxa in fossil material.

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Section: Speciation and Microevolutionmentioning

confidence: 99%

Evolution of the diatoms: insights from fossil, biological and molecular data

2006

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“…The physiological requirements of an algal taxon may be more accurately assessed when individuals are acquired from the area of interest, as diatoms can develop several distinct ecotypes over time and hence a particular species could have different resource requirements depending upon its system of origin (Guillard & Kilham, 1977;Lewis et al, 1997). Minimizing the length of time in culture may also improve the accuracy of physiological data because when diatoms are in culture for extended periods of time and sexual reproduction is not induced, cells can fall below the size of sexual induction and still survive, unlike under natural conditions (Round, 1993).…”

Section: Introductionmentioning

confidence: 99%

Resource requirements of four freshwater diatom taxa determined by in situ growth bioassays using natural populations from alpine lakes

et al. 2006

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We performed a series of in situ batch culture experiments to assess the resource requirements of common diatom taxa in alpine lakes of the central Rocky Mountains of North America. While physiological data are available on the resource requirements of some of these taxa, it is unclear whether intraspecific generalizations can be made across aquatic systems due to the potential development of ecotypes. In these experiments, we used amended lake water for a culture medium and natural diatom populations. Growth kinetics were determined for Asterionella formosa Hassall, Fragilaria crotonensis Kitton, Staurosirella pinnata (Ehr.) Williams and Round and Tetracyclus glans (Ehr.) Mills. Staurosirella pinnata, a historically abundant alpine diatom, had very low N and P requirements. Asterionella formosa and F. crotonensis, generally considered meso-or eutrophic species, exhibited low P requirements if N and Si were in moderate supply. Tetracyclus glans had the highest Si requirement. These experiments reveal that the recent changes in diatom community structure in these alpine lakes may be driven by changes in nutrient supply. We suggest that local diatom taxa and a natural culturing medium should be used to obtain more representative algal physiological data from a particular area.

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“…This concept has been challenged in recent years. Molecular approaches demonstrated that genetic diversity can be important and highly structured in marine species (Palumbi 1994, Knowlton 2000, Norris 2000, including phytoplanktonic organisms belonging to distinct phylogenetic lineages (Medlin et al 1996, Lewis et al 1997, Bolch et al 1999, LaJeunesse 2001, Montresor et al 2003. Gene flow within large populations of pelagic species with high dispersal potential can be non-homogeneous, and genetic structuring is evident over the biogeographic distribution range, matching oceanic provinces, water masses and/or possible dispersal routes (Scholin et al 1995, Bucklin et al 1998.…”

Section: Introductionmentioning

confidence: 99%

Toxic Pseudo-nitzschia multistriata (Bacillariophyceae) from the Gulf of Naples: morphology, toxin analysis and phylogenetic relationships with other Pseudo-nitzschia species

et al. 2002

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The genus Pseudo-nitzschia includes a number of species responsible for blooms in coastal and open waters worldwide. P. delicatissima, a species reported as a potential source of amnesic shellfish poisoning (ASP), reaches high concentrations in the Gulf of Naples (Mediterranean Sea), where it regularly blooms in spring and, at times, in autumn. We assessed both intra-and interindividual genetic diversity of this species before and during a bloom (February to April 2001) by sequencing the internal transcribed spacer regions (ITS1 and ITS2) and the 5.8S gene of the nuclear ribosomal DNA. PCR products obtained from 70 strains were cloned and several ITS copies were sequenced for each strain to assess intra-individual polymorphism. Phylogenies showed the presence of 5 distinct, well-supported lineages within what was considered to be a single morphospecies. Genetic diversity was higher in pre-bloom conditions, while all strains collected at the height of the bloom clustered within a single major clade. Ultrastructural investigations carried out on selected strains revealed morphological features slightly different from the ones typical for P. delicatissima only in 1 strain, outside the major clade. Our results, supported by the analysis of the hypervariable domains of LSU (large subunit) rDNA carried out on selected strains, suggest the presence of cryptic diversity within P. delicatissima. Such diversity could in fact explain the existence of toxic and nontoxic strains within the same species and the occasional mismatches between 'species-specific' molecular probes and target species. KEY WORDS: Diatoms · Pseudo-nitzschia delicatissima · ITS nDNA · Cryptic diversity · BloomResale or republication not permitted without written consent of the publisher

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Genetic variation in the diatomFragilaria capucina (Fragilariaceae) along a latitudinal gradient across North America

Cited by 40 publications

References 32 publications

Evolution of the diatoms: insights from fossil, biological and molecular data

Evolution of the diatoms: insights from fossil, biological and molecular data

Resource requirements of four freshwater diatom taxa determined by in situ growth bioassays using natural populations from alpine lakes

Toxic Pseudo-nitzschia multistriata (Bacillariophyceae) from the Gulf of Naples: morphology, toxin analysis and phylogenetic relationships with other Pseudo-nitzschia species

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