Search results for "Genetic drift"

The Genetic Legacy of Religious Diversity and Intolerance: Paternal Lineages of Christians, Jews, and Muslims in the Iberian Peninsula

2008

12 páginas, 6 figuras.-- et al.

Plant speciation in continental island floras as exemplified byNigellain the Aegean Archipelago

2008

Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of geographical isolation on non-adaptive radiation and allopatric speciation brought about by genetic drift. The Aegean Archipelago forms a highly fragmented complex of mostly continental shelf islands that have become disconnected from each other and the mainland in relatively recent geological times (ca<5.2 Ma). These ecologically fairly homogenous islands thus provide a suitable biogeographic context for assessing the relative influences of past range fragmentation, colonization, gene flow and drift on taxon diversification. Indeed, recent molecular biogeographic studies…

Genetic Diversity, Population Size, and Fitness in Central and Peripheral Populations of a Rare Plant Lychnis viscaria

1999

: Genetic diversity is expected to decrease in small and isolated populations as a consequence of bottlenecks, founder effects, inbreeding, and genetic drift. The genetics and ecology of the rare perennial plant Lychnis viscaria (Caryophyllaceae) were studied in both peripheral and central populations within its distribution area. We aimed to investigate the overall level of genetic diversity, its spatial distribution, and possible differences between peripheral and central populations by examining several populations with electrophoresis. Our results showed that the level of genetic diversity varied substantially among populations (  Hexp = 0.000–0.116) and that the total level of genetic …

Genetic Diversity and Evolution of Viral Populations

2021

Abstract Population genetic diversity plays a prominent role in viral evolution, pathogenesis, immune escape, and drug resistance. Different mechanisms are responsible for creating and maintaining genetic diversity in viruses, including error-prone replication, repair avoidance, and genome editing, among others. This diversity is subsequently modulated by natural selection and random genetic drift, whose action in turn depends on multiple factors including viral genetic architecture, viral demography, and ecology. Understanding these processes should contribute to the development of more efficient control and treatment strategies against viral pathogens.

Sex ratio, reproductive mode and genetic diversity inTriops cancriformis

2009

SUMMARY 1. Aquatic invertebrates display a wide array of alternative reproductive modes from apomixis to hermaphroditism and cyclical parthenogenesis. These have important effects on genetic diversity and population structure. Populations of the ‘living fossil’ Triops cancriformis display a range of sex ratios, and various reproductive modes are thought to underlie this variation. Using sex ratio information and histological analyses European populations have been inferred to be gonochoric (with separate males and females), selfing hermaphroditic and androdioecious, a rare reproductive mode in which selfing hermaphrodites coexist with variable proportions of males. In addition, some populat…

Characterization of Cryphonectria parasitica populations in Southern Italy

2005

Mitochondrial DNA evolution in experimental populations of Drosophila subobscura.

1990

When two mitochondrial DNA (mtDNA) haplotypes of Drosophila subobscura compete in experimental populations with discrete generations, one or the other approaches fixation, depending on the nuclear background with which they are associated. The approach to fixation, however, is strongly dependent on the effective number of females in the population, Nf. Whether or not the ultimate fate of a given mtDNA haplotype is determined by random genetic drift depends on Nf as well as on the relative fitnesses. Our experimental results show that the mtDNA polymorphisms observed in natural populations are affected by interactions among nuclear polymorphisms, random genetic drift, and direct selection on…

GroEL and the maintenance of bacterial endosymbiosis

2004

Many eukaryotic organisms have symbiotic associations with obligate intracellular bacteria. The clonal transmission of endosymbionts between host generations should lead to the irreversible fixation of slightly deleterious mutations in their non-recombinant genome by genetic drift. However, the stability of endosymbiosis indicates that some mechanism is involved in the amelioration of the effects of these mutations. We propose that the chaperone GroEL was involved in the acquisition of an endosymbiotic lifestyle not only by means of its over-production, as proposed by Moran, but also by its adaptive evolution mediated by positive selection to improve the interaction with the unstable endosy…

Mitochondrial DNA distributions indicate colony propagation by single matri-lineages in the social spider Stegodyphus dumicola (Eresidae)

2002

Colony-dwelling social spiders of the genus Stegodyphus are characterized by high colony turnover, within-colony mating, inbreeding and skewed sex ratios. These phenomena may purge genetic variation from the entire species gene pool. Social Stegodyphus have previously been discussed as ecologically unstable and evolutionary dead ends. We investigated the distribution and age (sequence divergence) of mitochondrial DNA variation for inferences of colony propagation, colony discreteness and maintenance of genetic variation in the social spider S. dumicola. In contrast to our expectations, we found abundant mtDNA variation, consisting of 15 haplotypes belonging to four haplotype lineages. Linea…

Experimental Evolution and Population Genetics of RNA Viruses

2009

Viral studies have contributed substantially to the field of experimental evolution during the last two decades. The rapid evolution of RNA viruses makes them especially suitable for investigating real-time evolution, while their small genomes facilitate the analysis of the genetic basis of evolutionary change. We review recent advances in RNA virus experimental evolution, focusing on genetic properties that differentiate them from DNA-based organisms, such as their high mutation rates, small genome sizes, low genetic robustness, and the predominance of antagonistic epistasis. We argue that these properties can explain many aspects of RNA virus evolution, including rapid evolution, marked f…