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Diploid Populations (diploid + population)
Selected AbstractsIntraspecific genome size variation and morphological differentiation of Ranunculus parnassifolius (Ranunculaceae), an Alpine,Pyrenean,Cantabrian polyploid groupBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010EDUARDO CIRES The aim of this study was to assess genome size variation and multivariate morphometric analyses to ascertain cytotype distribution patterns and the morphological differentiation within the Ranunculus parnassifolius group in the Pyrenees and the Alps. Although divergences in nuclear DNA content among different species within a genus are widely acknowledged, intraspecific variation is still a somewhat controversial issue. Holoploid and monoploid genome sizes (C- and Cx-values) were determined using propidium iodide flow cytometry in 125 plants of R. parnassifolius s.l. distributed across four European countries. Three different DNA ploidy levels were revealed in the study area: diploid (2n , 2x, 57.14%), triploid (2n , 3x, 1.19%), and tetraploid (2n , 4x, 41.67%). The mean population 2C-values ranged from 8.15 pg in diploids to 14.80 pg in tetraploids, representing a ratio of 1 : 1.8. Marked intraspecific/interpopulation differences in nuclear DNA content were found. Diploid populations prevail in the Pyrenees, although tetraploid cytotypes were reported throughout the distribution area. In general, mixed-cytotype populations were not found. The Spearman correlation coefficient did not reveal significant correlations between genome size and altitude, longitude, or latitude. Morphometric analyses and cluster analyses based on genome size variation revealed the presence of three major groups, which exhibited a particular biogeographical pattern. A new cytotype, DNA triploid, was found for the first time. Tetraploid populations showed constant nuclear DNA levels, whereas diploid populations from the Pyrenees, in which introgressive hybridization is suggested as a presumable trigger for genome size variation, did not. Scenarios for the evolution of geographical parthenogenesis in R. parnassifolius s.l. are discussed. Finally, the different levels of effectiveness between plant and animal reference standards are analysed. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 251,271. [source] Modelling the establishment and spread of autotetraploid plants in a spatially heterogeneous environmentJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2004B.-H. Li Abstract The establishment and spread of autotetraploids from an original diploid population in a heterogeneous environment were studied using a stochastic simulation model. Specifically, we investigated the effects of heterogeneous habitats and nonrandom pollen/seed dispersal on the critical value (,) of unreduced 2n gamete production necessary for the establishment of autotetraploids as predicted by deterministic models. Introduction of a heterogeneous environment with random pollen/seed dispersal had little effect on the , value. In contrast, incorporating nonrandom pollen/seed dispersal into a homogeneous environment considerably reduced the , value. Incorporating both heterogeneous habitats and nonrandom pollen/seed dispersal may lead either to an increase or to a decrease in the , value compared to that with random dispersal, indicating that the two factors interact in a complex way. [source] The role of triploid hybrids in the evolutionary dynamics of mixed-ploidy populationsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2004BRIAN C. HUSBAND Theory suggests that the evolution of autotetraploids within diploid populations will be opposed by a minority-cytotype mating disadvantage. The role of triploids in promoting autotetraploid establishment is rarely considered, yet triploids are often found in natural populations and are formed in experimental crosses. Here, I evaluate the effects of triploids on autotetraploid evolution using computer simulations and by synthesizing research on the evolutionary dynamics of mixed-ploidy populations in Chamerion angustifolium (Onagraceae). Simulations show that the fate of a tetraploid in a diploid population varies qualitatively depending on the relative fitness of triploids, the ploidy of their gametes and the fitness of diploids relative to tetraploids. In general, even partially fit triploids can increase the likelihood of diploid,tetraploid coexistence and, in some cases, facilitate tetraploid fixation. Within the diploid,tetraploid contact zone of C. angustifolium, mixed populations are common (43%), and often (39%) contain triploids. Greenhouse and field studies indicate that triploid fitness is low (9% of diploids) but variable. Furthermore, euploid gametes produced by triploids can be x, 2x or 3x and contribute the majority (62%) of new polyploids formed in each generation (2.3 × 10,3). Although triploid bridge, alone, may not account for the evolution of autotetraploidy in C. angustifolium, it probably contributes to the prevalence of mixed-ploidy populations in this species. Therefore, in contrast to hybrids in homoploid species, triploids may actually facilitate rather than diminish the fixation of tetraploids by enhancing the rate of formation. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82, 537,546. [source] Genetic analysis of offspring from intra- and interspecific crosses of Carassius auratus gibelio by chromosome and RAPD analysisJOURNAL OF FISH BIOLOGY, Issue 3 2005B. Tóth The ploidy of silver crucian carp Carassius auratus gibelio individuals, originating from nine natural habitats of Hungary, was estimated by erythrocyte nucleus area analysis. On the basis of DNA polymorphism, the genetic homogeneity or heterogeneity and the chromosome number of different offspring derived from the crossing of triploid and diploid populations and of two types of silver crucian carp females with other cyprinid males (Cyprinus carpio, Carassius carassius, Carassius auratus and Barbus conchonius) were determined. The results of chromosome and RAPD analysis demonstrated that diploid females could reproduce sexually with silver crucian carp and other cyprinid males and that the offspring of intra- and interspecific crosses contained the paternal DNA. Triploid females usually reproduced by gynogenesis and their offspring were clones, however, in very rare cases paternal genes were actually transmitted (i.e. paternal leakage) to the offspring and the progeny were triploid interspecific hybrids. RAPD analysis showed that while the paternal DNA appeared in the offspring, the maternal phenotype was strongly expressed. [source] Variations of 18S rDNA Loci Among Six Populations of Paeonia obovata Maxim. (Paeoniaceae) Revealed by Fluorescence In Situ HybridizationJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 5 2006Rui Luo Abstract The localization of 18S ribosomal RNA genes (rDNA) by fluorescence in situ hybridization (FISH) had been performed for some species of Paeonia. However, the pattern of 18S rDNA loci among populations is indistinct. In the present study, we localized 18S rDNA loci on meiotic or mitotic chromosomes of six populations of Paeonia obovata Maxim. (Paeoniaceae). Different numbers of rDNA loci were found with different diploid (2n=10) populations, namely eight (Lushi and Mt. Jiuhua populations), 10 (Mt. Taibai population), and seven (Mt. Guandi population), whereas tetraploid (2n=20) populations were all found with 16 loci. All rDNA loci were mapped near telomeres of mitotic chromosomes and there was no chromosome with two loci. The present results show that molecular cytological polymorphism exists among P. obovata diploid populations, indicating that structural variations occurred frequently during the evolutionary history of this species, accompanied with differentiation among populations. (Managing editor: Wei Wang) [source] Patterns, sources and ecological implications of clonal diversity in apomictic Ranunculus carpaticola (Ranunculus auricomus complex, Ranunculaceae)MOLECULAR ECOLOGY, Issue 4 2006O. PAUN Abstract Sources and implications of genetic diversity in agamic complexes are still under debate. Population studies (amplified fragment length polymorphisms, microsatellites) and karyological methods (Feulgen DNA image densitometry and flow cytometry) were employed for characterization of genetic diversity and ploidy levels of 10 populations of Ranunculus carpaticola in central Slovakia. Whereas two diploid populations showed high levels of genetic diversity, as expected for sexual reproduction, eight populations are hexaploid and harbour lower degrees of genotypic variation, but maintain high levels of heterozygosity at many loci, as is typical for apomicts. Polyploid populations consist either of a single AFLP genotype or of one dominant and a few deviating genotypes. genotype/genodive and character incompatibility analyses suggest that genotypic variation within apomictic populations is caused by mutations, but in one population probably also by recombination. This local facultative sexuality may have a great impact on regional genotypic diversity. Two microsatellite loci discriminated genotypes separated by the accumulation of few mutations (,clone mates') within each AFLP clone. Genetic diversity is partitioned mainly among apomictic populations and is not geographically structured, which may be due to facultative sexuality and/or multiple colonizations of sites by different clones. Habitat differentiation and a tendency to inhabit artificial meadows is more pronounced in apomictic than in sexual populations. We hypothesize that maintenance of genetic diversity and superior colonizing abilities of apomicts in temporally and spatially heterogeneous environments are important for their distributional success. [source] Polyploidy, phylogeography and Pleistocene refugia of the rockfern Asplenium ceterach: evidence from chloroplast DNAMOLECULAR ECOLOGY, Issue 10 2002S. A. Trewick Abstract Chloroplast DNA sequences were obtained from 331 Asplenium ceterach plants representing 143 populations from throughout the range of the complex in Europe, plus outlying sites in North Africa and the near East. We identified nine distinct haplotypes from a 900 bp fragment of trnL-trnF gene. Tetraploid populations were encountered throughout Europe and further afield, whereas diploid populations were scarcer and predominated in the Pannonian-Balkan region. Hexaploids were encountered only in southern Mediterranean populations. Four haplotypes were found among diploid populations of the Pannonian-Balkans indicating that this region formed a northern Pleistocene refugium. A separate polyploid complex centred on Greece, comprises diploid, tetraploid and hexaploid populations with two endemic haplotypes and suggests long-term persistence of populations in the southern Mediterranean. Three chloroplast DNA (cpDNA) haplotypes were common among tetraploids in Spain and Italy, with diversity reducing northwards suggesting expansion from the south after the Pleistocene. Our cpDNA and ploidy data indicate at least six independent origins of polyploids. [source] Intraspecific genome size variation and morphological differentiation of Ranunculus parnassifolius (Ranunculaceae), an Alpine,Pyrenean,Cantabrian polyploid groupBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010EDUARDO CIRES The aim of this study was to assess genome size variation and multivariate morphometric analyses to ascertain cytotype distribution patterns and the morphological differentiation within the Ranunculus parnassifolius group in the Pyrenees and the Alps. Although divergences in nuclear DNA content among different species within a genus are widely acknowledged, intraspecific variation is still a somewhat controversial issue. Holoploid and monoploid genome sizes (C- and Cx-values) were determined using propidium iodide flow cytometry in 125 plants of R. parnassifolius s.l. distributed across four European countries. Three different DNA ploidy levels were revealed in the study area: diploid (2n , 2x, 57.14%), triploid (2n , 3x, 1.19%), and tetraploid (2n , 4x, 41.67%). The mean population 2C-values ranged from 8.15 pg in diploids to 14.80 pg in tetraploids, representing a ratio of 1 : 1.8. Marked intraspecific/interpopulation differences in nuclear DNA content were found. Diploid populations prevail in the Pyrenees, although tetraploid cytotypes were reported throughout the distribution area. In general, mixed-cytotype populations were not found. The Spearman correlation coefficient did not reveal significant correlations between genome size and altitude, longitude, or latitude. Morphometric analyses and cluster analyses based on genome size variation revealed the presence of three major groups, which exhibited a particular biogeographical pattern. A new cytotype, DNA triploid, was found for the first time. Tetraploid populations showed constant nuclear DNA levels, whereas diploid populations from the Pyrenees, in which introgressive hybridization is suggested as a presumable trigger for genome size variation, did not. Scenarios for the evolution of geographical parthenogenesis in R. parnassifolius s.l. are discussed. Finally, the different levels of effectiveness between plant and animal reference standards are analysed. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 251,271. [source] Allopolyploidy and homoploid hybridization in the Sphagnum subsecundum complex (Sphagnaceae: Bryophyta)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010MARIANA RICCA Several complexes of species in Sphagnum (peat mosses) originated through hybridization and allopolyploidy, suggesting that these processes have played a major evolutionary role in this genus. The Sphagnum subsecundum complex includes gametophytically haploid and diploid species in North America. Analyses of 12 microsatellite loci and sequences from two plastid DNA markers show that the evolutionary history of this group is substantially more complex than previously thought. Two taxonomic species, Sphagnum lescurii and Sphagnum inundatum, include both haploid and diploid populations. Within each ploidal level, S. lescurii and S. inundatum are not genetically differentiated. The diploid taxa show patterns of fixed heterozygosity for the microsatellite markers, consistent with an allopolyploid origin. Diploid S. lescurii is an allopolyploid between haploid S. lescurii and (haploid) S. subsecundum. Sphagnum carolinianum is an allopolyploid between haploid S. lescurii and an unknown parent. We detected homoploid hybridization between the haploids Sphagnum contortum and S. subsecundum. Finally, we report three samples of diploid Sphagnum platyphyllum (otherwise haploid) that have an allopolyploid origin involving north-eastern haploid S. platyphyllum and an unidentified taxon. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 135,151. [source] The role of triploid hybrids in the evolutionary dynamics of mixed-ploidy populationsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2004BRIAN C. HUSBAND Theory suggests that the evolution of autotetraploids within diploid populations will be opposed by a minority-cytotype mating disadvantage. The role of triploids in promoting autotetraploid establishment is rarely considered, yet triploids are often found in natural populations and are formed in experimental crosses. Here, I evaluate the effects of triploids on autotetraploid evolution using computer simulations and by synthesizing research on the evolutionary dynamics of mixed-ploidy populations in Chamerion angustifolium (Onagraceae). Simulations show that the fate of a tetraploid in a diploid population varies qualitatively depending on the relative fitness of triploids, the ploidy of their gametes and the fitness of diploids relative to tetraploids. In general, even partially fit triploids can increase the likelihood of diploid,tetraploid coexistence and, in some cases, facilitate tetraploid fixation. Within the diploid,tetraploid contact zone of C. angustifolium, mixed populations are common (43%), and often (39%) contain triploids. Greenhouse and field studies indicate that triploid fitness is low (9% of diploids) but variable. Furthermore, euploid gametes produced by triploids can be x, 2x or 3x and contribute the majority (62%) of new polyploids formed in each generation (2.3 × 10,3). Although triploid bridge, alone, may not account for the evolution of autotetraploidy in C. angustifolium, it probably contributes to the prevalence of mixed-ploidy populations in this species. Therefore, in contrast to hybrids in homoploid species, triploids may actually facilitate rather than diminish the fixation of tetraploids by enhancing the rate of formation. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82, 537,546. [source] | ||||||||||