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  • 1
    Keywords: Life sciences ; Biochemistry ; Evolution (Biology) ; Plant breeding ; Life sciences ; Evolutionary Biology ; Plant Genetics & Genomics ; Plant Biochemistry ; Springer eBooks
    Description / Table of Contents: 〈p〉Evolutionary Significance of Whole-Genome Duplication -- Genetic Consequences of Polyploidy in Plants -- Meiosis in polyploid plants -- Origins of Novel Phenotypic Variation in Polyploids -- Identifying the Phylogenetic Context of Whole-Genome Duplications in Plants -- Ancient and Recent Polyploidy in Monocots -- Genomic Plasticity in Polyploid Wheat -- Maize (〈i〉Zea mays〈/i〉) as a model for studying the impact of gene and regulatory sequence loss following whole genome duplication -- Polyploidy in legumes -- Jeans, genes, and genomes: cotton as a model for studying polyploidy.-Evolutionary implications of genome and karyotype restructuring in 〈i〉Nicotiana tabacum〈/i〉 L -- Polyploid evolution in 〈i〉Spartina〈/i〉: Dealing with highly redundant hybrid genomes -- Allopolyploid speciation in action: the origins and evolution of 〈i〉Senecio cambrensis -- 〈/i〉The early stages of polyploidy: rapid and repeated evolution in〈i〉 Tragopogon -- 〈/i〉Yeast as a window into changes in genome complexity due to polyploidization -- Two Rounds of Whole Genome Duplication: Evidence and Impact on the Evolution of Vertebrate Innovations -- Polyploidy in fish and the teleost genome duplication -- Polyploidization and sex chromosome evolution in amphibians.-〈/p〉
    Abstract: 〈p〉Polyploidy ́€“ whole-genome duplication (WGD) ́€“ is a fundamental driver of biodiversity with significant consequences for genome structure, organization, and evolution.℗ Once considered a speciation process common only in plants, polyploidy is now recognized to have played a major role in the structure, gene content, and evolution of most eukaryotic genomes.℗ In fact, the diversity of eukaryotes seems closely tied to multiple WGDs. Polyploidy generates new genomic interactions ́€“ initially resulting in ́€œgenomic and transcriptomic shocḱ€ ́€“ that must be resolved in a new polyploid lineage.℗ This process essentially acts as a ́€œreset́€ button, resulting in genomic changes that may ultimately promote adaptive speciation. 〈/p〉〈p〉℗ 〈/p〉〈p〉This book brings together for the first time the conceptual and theoretical underpinnings of polyploid genome evolution with syntheses of the patterns and processes of genome evolution in diverse polyploid groups.℗ Because polyploidy is most common and best studied in plants, the book emphasizes plant models, but recent studies of vertebrates and fungi are providing fresh perspectives on factors that allow polyploid speciation and shape polyploid genomes.℗ The emerging paradigm is that polyploidy ́€“ through alterations in genome structure and gene regulation ́€“ generates genetic and phenotypic novelty that manifests itself at the chromosomal, physiological, and organismal levels, with long-term ecological and evolutionary consequences.〈/p〉
    Pages: VIII, 415 p. 66 illus., 50 illus. in color. : digital.
    ISBN: 9783642314421
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  • 2
    ISSN: 1432-0983
    Keywords: Mitochondrial genome size ; Repeated sequences ; Ribosomal RNA genes ; Nonflowering plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report the first estimates of genome size and complexity for mitochondrial DNAs (mtDNAs) from nonflowering land plants. The mtDNA of Onoclea sensibilis (sensitive fern) is approximately 300 kb in size, while that of Equisetum arvense (common horsetail) is at least 200 kb. Sufficient mtDNA of Onoclea was available to permit an estimation of the copy number and a linkage analysis of nine mitochondrial genes. Six of these genes appear to be present in only one or two copies in the Onoclea genome, whereas three other genes are present in multiple copies. Five of the approximately ten genes encoding 26S rRNA are located on a large, 〉10kb, dispersed repeat that also contains closely linked genes for 18S rRNA and the alpha subunit of ATPase (atpA). The other 26S genes belong to a second dispersed repeat family of 〉8 kb whose elements do not contain any other identified genes. Because flowering plant mtDNAs are also large and contain dispersed, gene-containing, repeats, it appears that these features arose early in the evolution of land plants, or perhaps even in their green algal ancestors.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1615-6110
    Keywords: Intraspecific phylogeography ; biogeography ; cpDNA ; glacial refugia ; genetic structuring ; plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Molecular studies of plants from the Pacific Northwest of North America suggest a recurrent pattern of genetic differentiation and geographic structuring. In each of five angiosperms and one fern species representing diverse life histories, cpDNA data indicate two clades of populations that are geographically structured. A northern group comprises populations from Alaska to central or southern Oregon, whereas populations from central Oregon southward to northern California form a southern group. In several of these species, a few populations having southern genotypes may have survived in glacial refugia further north in the Olympic Peninsula, Queen Charlotte Islands, and Prince of Wales Island. Allozyme data reveal a similar pattern of differentiation in several other plants from the Pacific Northwest. North-south partitioning of genotypes has also been reported for several animal species from this region. On a broader geographic scale, northsouth partitioning of genotypes has also been observed in other plants from western North America having a variety of geographic distributions. Some species also display a reduction of genetic variability in the northern portion of their range compared to the south. The data suggest strongly that past glaciation profoundly influenced the genetic architecture of the flora and fauna of the Pacific Northwest. Two alternative hypotheses are advanced to explain the geographic structuring of genotypes. First, past glaciation may have created discontinuities in the geographic distributions of plant species, with populations surviving in several well-isolated northern and southern refugia. Following glaciation, migration of genetically differentiated, once-isolated populations resulted in the formation of a continuous geographic distribution with a major genetic discontinuity. Alternatively, plants survived and subsequently migrated northward from a southern refugium, and a genotype became fixed in one or a few populations at the leading edge of recolonization. Subsequent long-distance dispersal from this leading edge resulted in a relatively uniform northern genotype that differs from the southern genotype(s). Whatever the underlying mechanism, Pleistocence glaciation may have molded the intraspecific genetic architecture of both plants and animals from the Pacific Northwest in a geographically similar manner. Future studies should seek to obtain a comprehensive phylogeography for regions that includes a diversity of both plants and animals.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1615-6110
    Keywords: Apiaceae ; Lomatium ; Euryptera group ; ITS sequences ; molecular systematics ; phylogenetic analysis ; parsimony ; maximum likelihood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lomatium, the largest genus of Apiaceae in western North America, includes many narrow endemics whose relationships are uncertain. Although no infrageneric classification exists forLomatium, several informal groups have been recognized. TheEuryptera group comprises seven narrowly endemic species distributed primarily in California. We conducted parsimony and maximum likelihood (ML) analyses using sequences of the internal transcribed spacers (ITS) of the nuclear ribosomal DNA from species of theEuryptera group and several other species ofLomatium. When considered with distribution, morphological, and cpDNA data, the ITS analyses are consistent with the monophyly of theEuryptera group and suggests that speciation in this group has occurred through geographical divergence. Inferences from ITS data also identify putative progenitors of the polyploidEuryptera species.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1615-6110
    Keywords: Brassicaceae ; Draba ; Draba alpina complex ; Draba crassifolia ; Enzyme electrophoresis ; allopolyploidy ; fixed heterozygosity ; inbreeding ; multiple origins ; polyphyly ; phylogeny ; phytogeography ; Flora of Scandinavia ; Svalbard
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 104 populations of 15 Nordic species (2x–16x) of the taxonomically complex genusDraba were investigated using enzyme electrophoresis. The polyploids were genetic alloploids showing high levels of fixed heterozygosity and electrophoretic variation; the diploids were homozygous and genetically depauperate. Thus, the data suggest that alloploidy in arctic-alpineDraba serves as an escape from genetic depauperation caused by inbreeding at the diploid level. Although some populations probably have local alloploid origins, electrophoretic data indicate that several polyploids have migrated repeatedly into the Nordic area.Draba crassifolia (2n = 40) is probably octoploid based on x = 5. A hypothesis on the evolutionary history of the polyploids based on x = 8 is presented. Diploids contributing to numerous polyploid genomes and multiple origins of polyploids have seriously blurred taxonomic relationships. Relationships inferred from genetic data do not always correspond to those based on morphology; two morphologically very similar polyploids,D. alpina andD. oxycarpa, were, for example, genetically distant and probably represent independent lineages.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1615-6110
    Keywords: Asteridae ; Polemoniaceae ; 18S rDNA sequences ; systematics ; phylogenetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cladistic analyses of chloroplast DNA disagree with current classifications by placingPolemoniaceae near sympetalous families with two staminal whorls, includingFouquieriaceae andDiapensiaceae, rather than near sympetalous families with a single staminal whorl, such asHydrophyllaceae andConvolvulaceae. To explore further the affinities ofPolemoniaceae, we sequenced 18S ribosomal DNA for eight genera ofPolemoniaceae and 31 families representing a broadly definedAsteridae. The distribution of variation in these sequences suggest some sites are hypervariable and multiple hits at these sites have obscured much of the hierarchical structure present in the data. Nevertheless, parsimony, least-squares minimum evolution, and maximum likelihood methods all support a monophyleticPolemoniaceae that is placed nearFouquieriaceae, Diapensiaceae and related “ericalean” families.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 402 (1999), S. 402-404 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Comparative biology requires a firm phylogenetic foundation to uncover and understand patterns of diversification and evaluate hypotheses of the processes responsible for these patterns. In the angiosperms, studies of diversification in floral form, stamen organization, reproductive biology, ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant species biology 7 (1992), S. 0 
    ISSN: 1442-1984
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Although most species of homosporous pteridophytes investigated to date are highly outcrossing, there is little conclusive evidence of the mechanisms promoting intergametophytic matings in natural populations. The hormone antheridiogen, produced by meristematic and usually archegoniate gametophytes, has been implicated as an effective promoter of intergametophytic matings in natural populations. In this study, antheridiogen production and response were analyzed in laboratory-cultured gametophytes from five outcrossing populations of Gymnocarpium dryopteris ssp. disjunctum. The numbers of antheridia present in gametophytes grown on antheridiogen-enriched and control nutrient agar were recorded over an 84-day period; approximately 4200 gametophytes were observed. Contingency table analyses indicated a statistically significant positive response to treatment medium in the majority of cultures analyzed. However, consistently insignificant responses to treatment medium in two gametophyte cultures suggest intrapopulational variation in gametophytic response to antheridiogen. Antheridiogen production and response in gametophytes of G. dryopteris ssp. disjunctum suggest that this antheridiogen system effectively promotes intergametophytic matings in natural populations. The selection pressures under which antheridiogen systems may have evolved are also discussed.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1442-1984
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Breeding-system data have been available for a large number and diverse array of angio-sperms for a relatively long time. In contrast, breeding systems of ferns and their allies (pteridophytes) have only recently been examined, and breeding-system data from natural populations of sporophytes are still lacking for pteridophytes representing many life-history strategies. Few studies, for example, have examined breeding systems of tropical pteridophytes, and no breeding-system data are available for tree ferns. We therefore examined the breeding systems of three species of tree ferns from Costa Rica, Alsophila firma (Cyatheaceae), Cyathea stipularis (Cyatheaceae), and Lophosoria quadripinnata (Lophosoriaceae) using enzyme electro-phoresis. Genetic data were used to estimate intragametophytic self-fertilization and F, the fixation index. Analysis of genetic data indicates that the gametophytes of these three species predominantly cross-fertilize; all three species would be characterized as outcrossers. However, some population-to-population variation in breeding system was detected in all three species. Outcrossing also typifies a diverse array of temperate ferns. Thus, despite the potential for self-fertilization, outcrossing appears to characterize the majority of pteridophytes representing a variety of evolutionary lineages, life-history strategies, and environments.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant species biology 5 (1990), S. 0 
    ISSN: 1442-1984
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Mating systems of 18 species of homosporous ferns follow a bimodal distribution, similar to that observed for seed plants (Schemske and Lande, 1985). Most species are highly outcrossing, a few are inbreeding, and two species examined to date have mixed mating systems. Equisetum arvense and several species of lycopods are also highly outcrossing. Several mechanisms, including inbreeding depression, antheridiogen, and ontogenetic sequences that result in effectively unisexual gametophytes, promote outcrossing in homosporous ferns and perhaps other homosporous pteridophytes as well. In some species of homosporous ferns, selection has favored the evolution of inbreeding as an adaptation for colonization. High levels of intra- and interpopulational gene flow via spore dispersal, coupled with high levels of intergametophytic crossing, generally lead to genetically homogeneous populations and species of homosporous ferns. However, rock-dwelling ferns and ferns from xeric habitats may exhibit significant population genetic structure due to physically patchy habitats. Reticulate evolution in homosporous ferns may be enhanced by high levels of intergametophytic crossing.
    Type of Medium: Electronic Resource
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