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Polyploid Populations (polyploid + population)
Selected AbstractsPatterns, 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] A polyploid population of Saccharomyces cerevisiae with separate sexes (dioecy)FEMS YEAST RESEARCH, Issue 6 2010Rim Al Safadi Abstract Saccharomyces cerevisiae has proved to be an interesting model for studies of evolution, with whole-genome duplication shown to have played an important role in the evolution of this species. This phenomenon depends on the formation of a transient stable polyploid state. Previous studies have reported polyploidy to be an unstable state in yeast, but here, we describe a polyploid population of S. cerevisiae. The evolution of higher eukaryotes has also involved the development of different systems of sexual reproduction, the choice between self-fertilization and out-crossing becoming a key issue. Saccharomyces cerevisiae is a hermaphrodite eukaryote, despite the theoretical genetic disadvantages of this strategy, in which self-fertilization occurs. We describe, for the first time, a near-dioecious (with separate sexes) population in this species. Mating type and the MAT locus display complex segregations. Essentially, each strain produces, by meiosis, spores of only one mating type: mata or mat,. Moreover, strains are heterothallic, and diploid nonmating clones generated from a single spore do not sporulate. These three properties limit self-fertilization and strongly favour out-crossing. We suggest that the shift in sexual strategy, from hermaphroditism to dioecy, is specific to the brewing process, which overcomes the sexual isolation probably found in natural biotopes. [source] ECOLOGICAL DIFFERENTIATION AND DIPLOID SUPERIORITY ACROSS A MOVING PLOIDY CONTACT ZONEEVOLUTION, Issue 1 2007Richard J. A. Buggs Plant polyploid complexes provide useful model systems for distinguishing between adaptive and nonadaptive causes of parapatric distributions in closely related lineages. Polyploidy often gives rise to morphological and physiological changes, which may be adaptive to different environments, but separate distributions may also be maintained by reproductive interference caused by postzygotic reproductive isolation. Here, we test the hypothesis that diploid and descendent polyploid races of the wind-pollinated herb Mercurialis annua, which are found in parapatry over an environmental gradient in northeast Spain, are differentiated in their ecophysiology and life history. We also ask whether any such differences represent adaptations to their different natural environments. On the basis of a series of reciprocal transplant experiments in the field, and experiments under controlled conditions, we found that diploid and polyploid populations of M. annua are ecologically differentiated, but that they do not show local adaptation; rather, the diploids have higher fitness than the polyploids across both diploid- and polyploid-occupied regions. In fact, diploids are currently displacing polyploids by advancing south on two separate fronts in Spain, and previous work has shown that this displacement is being driven to a large extent by asymmetrical pollen swamping. Our results here suggest that ecophysiological superiority of the diploids may also be contributing to their expansion. [source] Patterns of recurrent evolution and geographic parthenogenesis within apomictic polyploid Easter daises (Townsendia hookeri)MOLECULAR ECOLOGY, Issue 11 2006STACEY LEE THOMPSON Abstract Geographic patterns of parthenogenesis and the number of transitions from sexual diploidy to asexual (apomictic) autopolyploidy were examined for 40 populations of the Easter daisy, Townsendia hookeri. Analyses of pollen diameter and stainability characterized 15 sexual diploid and 25 apomictic polyploid populations from throughout the plant's western North American range. Sexual diploids were restricted to two Wisconsin refugia: Colorado/Wyoming, south of the ice sheets, and northern Yukon/Beringia. Chloroplast DNA sequencing uncovered 17 polymorphisms within the ndhF gene and trnK intron, yielding 10 haplotypes. Phylogenetic analyses indicated that five exclusively polyploid haplotypes were derived from four haplotypes that are shared among ploidies, conservatively inferring a minimum of four origins of apomictic polyploidy. Three of these apomictic polyploid origins were derived from southern sexual diploids, while the fourth origin was derived from northern sexual diploids. Analyses of regional diversity were suggestive of a formerly broad distribution for sexual diploids that has become subsequently fragmented, possibly due to the last round of glaciation. As sexual diploids were exclusively found north and south of the glacial maximum, while formerly glaciated areas were exclusively inhabited by asexual polyploids derived from both northern and southern sexual lineages, it is more likely that patterns of glaciation, as opposed to a particular latitudinal trend, played a causal role in the establishment of the observed pattern of geographic parthenogenesis in Easter daisies. [source] Genetic similarity of polyploids: a new version of the computer program POPDIST (version 1.2.0) considers intraspecific genetic differentiationMOLECULAR ECOLOGY RESOURCES, Issue 5 2009JÜRGEN TOMIUK Abstract For evolutionary studies of polyploid species estimates of the genetic identity between species with different degrees of ploidy are particularly required because gene counting in samples of polyploid individuals often cannot be done, e.g., in triploids the phenotype AB can be genotypically either ABB or AAB. We recently suggested a genetic distance measure that is based on phenotype counting and made available the computer program POPDIST. The program provides maximum-likelihood estimates of the genetic identities and distances between polyploid populations, but this approach is not informative for populations within species that only differ in their allele frequencies. We now close this gap by applying the frequencies of shared ,bands' in both populations to Nei's identity measure. Our simulation study demonstrates the close correlation between the band-sharing identity and the genetic identity calculated on the basis of gene frequencies for any degree of ploidy. The new extended version of POPDIST (version 1.2.0) provides the option of choosing either the maximum-likelihood estimator or the band-sharing measure. [source] | ||||||||||