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Considerable Genetic Variation (considerable + genetic_variation)
Selected AbstractsDYNAMICS OF POLYPLOID FORMATION IN TRAGOPOGON (ASTERACEAE): RECURRENT FORMATION, GENE FLOW, AND POPULATION STRUCTUREEVOLUTION, Issue 7 2010V. Vaughan Symonds Polyploidy is a major feature of angiosperm evolution and diversification. Most polyploid species have formed multiple times, yet we know little about the genetic consequences of recurrent formations. Among the clearest examples of recurrent polyploidy are Tragopogon mirus and T. miscellus (Asteraceae), each of which has formed repeatedly in the last ,80 years from known diploid progenitors in western North America. Here, we apply progenitor-specific microsatellite markers to examine the genetic contributions to each tetraploid species and to assess gene flow among populations of independent formation. These data provide fine-scale resolution of independent origins for both polyploid species. Importantly, multiple origins have resulted in considerable genetic variation within both polyploid species; however, the patterns of variation detected in the polyploids contrast with those observed in extant populations of the diploid progenitors. The genotypes detected in the two polyploid species appear to represent a snapshot of historical population structure in the diploid progenitors, rather than modern diploid genotypes. Our data also indicate a lack of gene flow among polyploid plants of independent origin, even when they co-occur, suggesting potential reproductive barriers among separate lineages in both polyploid species. [source] Use of RAPD and ISSR Markers in Detection of Genetic Variation and Population Structure among Fusarium oxysporum f. sp. ciceris Isolates on Chickpea in TurkeyJOURNAL OF PHYTOPATHOLOGY, Issue 3 2008H. Bayraktar Abstract Genetic variation among the isolates of Fusarium oxysporum f. sp. ciceris, the causal agent of chickpea wilt worldwide, was analysed using pathogenicity tests and molecular markers , random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) polymorphism. Hundred and eight isolates were obtained from diseased chickpea plants in 13 different provinces of Turkey, out of which 74 isolates were assessed using 30 arbitrary decamer primers and 20 ISSR primers. Unweighted pair-grouped method by arithmetic average cluster analysis of RAPD, ISSR and RAPD + ISSR datasets provided a substantially similar discrimination among Turkish isolates and divided into three major groups. Group 1, 2 and 3 consisted of 41, 18 and 15 isolates, respectively. These methods revealed a considerable genetic variation among Turkish isolates, but no correlation with regard to the clustering of isolates from different geographic regions. Analysis of molecular variance confirmed that most genetic variability resulted from the differences among isolates within regions. Our results also indicated that the low-genetic differentiation (FST) and high gene flow (Nm) among populations had a significant effect on the emergence and evolutionary development of F. oxysporum f. sp. ciceris. This is the first report on genetic diversity and population structure of F. oxysporum isolates on chickpea in Turkey. [source] Comparisons of Isolates of Fusarium avenaceum from White Lupin and Other Crops by Pathogenicity Tests, DNA Analyses and Vegetative Compatibility TestsJOURNAL OF PHYTOPATHOLOGY, Issue 4 2000K. Satyaprasad Isolates of Fusarium avenaceum, mostly from crops of white lupin or wheat, were tested for pathogenicity on white lupin and wheat plants and compared by DNA tests and, in a limited study, vegetative compatibility. Most of the 80 isolates were pathogenic on both plant species after inoculation on shoot bases. Disease severity was greater at higher incubation temperatures that ranged from 15/10°C to 25/20°C (day/night temperatures). Isolates from lupin crops tended to be more pathogenic, on average, on lupins than on cereals. Polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analysis of the internal transcribed spacer region of the rDNA distinguished two groups of isolates that occurred in different proportions among isolates from lupins and cereal crops. Random amplified polymorphic DNA (RAPD)-PCR analyses indicated considerable genetic variation among isolates, but there was some similarity among groups of isolates from populations in the same field. Genetic diversity was confirmed by a high degree of vegetative incompatibility among 20 isolates using nitrate nonutilizing mutants. There were no relationships among pathogenicity, RFLP group, RAPD group and vegetative compatibility group. Zusammenfassung Fusarium-avenaceum -Isolate, die überwiegend von Weißier Lupine oder Weizen stammten, wurden hinsichtlich ihrer Pathogenität für Weißie Lupine und Weizenpflanzen getestet und durch DNA-Tests verglichen. In einer kleineren Studie wurde zudem ihre vegetative Kompatibilität geprüft. Die meisten der 80 Isolate waren nach Inokulation der Stengel-bzw. Halmbasis für beide Pflanzenarten pathogen. Bei hohen Inkubationstemperaturen im Bereich von 15/10°C bis 25/20°C (Tag/Nacht-Temperaturen) war der Befall stärker. Von Lupinen stammende Isolate waren im Durchschnitt stärker pathogen für Lupinen als für Getreide. Eine PCR-RFLP-Analyse der Internal-transcribed-spacer-Region der rDNA teilte die Isolate in zwei Gruppen, die bei den Isolaten von Lupinen und Getreide in verschiedenen Anteilen vertreten waren. RAPD-PCR-Analysen zeigten eine beträchtliche genetische Variation bei den Isolaten, aber auch gewisse Ähnlichkeiten bei den Isolatgruppen, die von Populationen im selben Feld stammten. Die genetische Diversität wurde auch durch ein hohes Ausmaßi an vegetativer Inkompatibilität bei 20 Isolaten deutlich; hier wurden Nitrat nicht verwertende Mutanten verwendet. Zwischen Pathogenität, RFLP-Gruppe, RAPD-Gruppe und vegetativer Kompatibilitätsgruppe bestanden keine Beziehungen. [source] Genetic divergence and migration patterns in a North American passerine bird: implications for evolution and conservationMOLECULAR ECOLOGY, Issue 8 2006LESLIE A. DAVIS Abstract Like many other migratory birds, the black-throated blue warbler (Dendroica caerulescens) shows pronounced differences in migratory behaviour and other traits between populations: birds in the southern part of the breeding range have darker plumage and migrate to the eastern Caribbean during the winter, whereas those in the north have lighter plumage and migrate to the western Caribbean. We examined the phylogeography of this species, using samples collected from northern and southern populations, to determine whether differentiation between these populations dates to the Pleistocene or earlier, or whether differences in plumage and migratory behaviour have arisen more recently. We analysed variation at 369 bp of the mitochondrial control region domain I and also at seven nuclear microsatellites. Analyses revealed considerable genetic variation, but the vast majority of this variation was found within rather than between populations, and there was little differentiation between northern and southern populations. Phylogeographic analyses revealed a very shallow phylogenetic tree, a star-like haplotype network, and a unimodal mismatch distribution, all indicative of a recent range expansion from a single refugium. Coalescent modelling approaches also indicated a recent common ancestor for the entire group of birds analysed, no split between northern and southern populations, and high levels of gene flow. These results show that Pleistocene or earlier events have played little role in creating differences between northern and southern populations, suggesting that migratory and other differences between populations have arisen very recently. The implications of these results for the evolution of migration and defining taxonomic groups for conservation efforts are discussed. [source] Fine-scale population structure and dispersal in Biomphalaria glabrata, the intermediate snail host of Schistosoma mansoni, in VenezuelaMOLECULAR ECOLOGY, Issue 5 2002J. Mavárez Abstract Biomphalaria glabrata is the main intermediate host of Schistosoma mansoni in America and one of the most intensely studied species of freshwater snails, yet very little is known about its population biology. Here, we used seven highly polymorphic microsatellite loci to analyse genetic diversity in the Valencia lake basin, which represents the core of the endemic area for schistosomiasis in Venezuela. Populations were sampled at short spatial scale (a few kilometres), both inside the lake and in ponds or rivers near the lake. Our results indicate that B. glabrata essentially cross-fertilizes, with little variation in selfing rates among populations. Our markers detected considerable genetic variation, with an average heterozygosity of 0.60. More diversity per population was found within than outside the lake, suggesting an influence of connectivity among populations on the levels of genetic diversity. A marked population structure was detected and lake populations were less structured than other populations. Most individuals were assigned to their population of origin using an assignment test. No strong demographic signal (e.g. bottleneck) was detected, though lake populations are likely to experience bottlenecks more frequently than the other populations analysed. Differences in gene flow therefore seem to play an important role in population differentiation and in the restoring of genetic diversity in demographically unstable populations. [source] Eight polymorphic microsatellite loci markers for the barnacle Balanus amphitrite (syn. Amphibalanus amphitrite) Darwin 1854MOLECULAR ECOLOGY RESOURCES, Issue 1 2009M. A. ROBSON Abstract Balanus amphitrite is a widespread species of barnacle. It is frequently studied, and of great importance to the marine coatings industry due to its significant abundance as a fouling organism on commercial shipping. We isolated and characterized eight highly polymorphic microsatellite loci, to aid in the determination of population genetic structure within this species. All loci showed considerable genetic variation with the number of alleles ranging from two to 14. Expected heterozygosity ranged from 0.74 to 0.98. [source] | ||||||||||