Search results for "population genetics."
showing 10 items of 248 documents
Large Hardy-Weinberg equilibrium deviations in the Daphnia longispina of Lake El Tobar
1995
The population structure of Daphnia longispina in Lake El Tobar, Spain was studied by measuring variation at the aldehyde oxidase (AO), phosphoglucose isomerase (PGI) and phosphoglucose mutase (PGM) loci in each of 1337 individuals from four collections. In 9 of the 12 comparisons between observed allele frequencies and those expected by Hardy-Weinberg equilibrium there was an excess of heterozygotes. We found 27 of the potential number of 54 composite electromorphs (‘clones’) based on the three allozymes. Clone diversities were rather high in all collections. Three clones reached frequencies of over 25% and different clones were dominant in each of the four collections. Strong temporal var…
Invasion success despite reduction of genetic diversity in the European populations of eastern mosquitofish (Gambusia holbrooki)
2006
The introduction of a few individuals to new, isolated habitats (founder effect) is expected to reduce the genetic variability of a population. At the beginning of the last century a few eastern mosquitofish (Gambusia holbrooki) individuals were introduced to Southern Europe from North America to control malaria‐carrying mosquitoes. We studied the effect of this severe bottleneck on genetic variability in four populations of eastern mosquitofish introduced to Spain and Italy in the early 1900s and compared them to a native population in North America. Using amplified polymorphic DNA–polymerase chain reaction (RADP–PCR) we found a strong reduction of genetic diversity, in terms of both numbe…
Genetic differentiation and structure of Hippocrepis valentina (Leguminosae) populations
2000
We present an analysis of isozyme variability in natural populations of the plant species Hippocrepis valentina (Leguminosae), which is endemic to the eastern Mediterranean coast of Spain and currently has endangered species status. Our results, obtained by starch-gel electrophoresis of 15 loci, show normal levels of variability for species with similar biology. The comparison with the patterns of genetic variability of two closely related species, H. balearica and H. grosii, confirms the taxonomic status of H. valentina as a proper species, independent of H. balearica, as previously suggested. The analysis of population subdivision shows that substantial variation among populations is pres…
A population genetics view of animal domestication
2012
The fundamental shift associated with the domestication of plants and animals allowed for a dramatic increase in human population sizes and the emergence of modern society. Despite its importance and the decades of research devoted to studying it, questions regarding the origins and processes of domestication remain. Here, we review recent theoretical advances and present a perspective that underscores the crucial role that population admixture has played in influencing the genomes of domestic animals over the past 10000 years. We then discuss novel approaches to generating and analysing genetic data, emphasising the importance of an explicit hypothesis-testing approach for the inference of…
New Polymorphic Microsatellite Loci for the Zebra MusselDreissena polymorpha(Pallas, 1771), a Common Bioindicator
2011
ABSTRACT To investigate the influence of environmental pollution on the population genetics of Dreissena polymorpha, we developed five new polymorphic micro satellite loci for the zebra mussel. This mussel is widely distributed and is a common bioindicator in the field of ecotoxicology. The amplification of the microsatellite loci was tested on a single population of 24 individuals. In this population, the number of alleles per locus ranged from 3–14, and the observed heterozygosity ranged from 0.545–0.909 (mean, 0.772). All loci followed Hardy-Weinberg expectations, suggesting no evidence for null alleles. There was no significant genetic linkage disequilibrium, neither between the aforeme…
Comparative population genetic structures of the fruit flyUrophora carduiand its primary parasitoidEurytoma robusta
2003
The interaction between two species may depend on geographic scale and this in turn can affect co-evolution among them. The present study comparatively examines population genetic structures of the tephritid gall fly Urophora cardui and its primary ectoparasitoid Eurytoma robusta for inference of relative dispersal patterns and host parasitoid specificity. Genetic differentiation patterns indicated two levels of hierarchical structure in both species: locally similar distance-dependencies but globally differences. Locally, both species showed isolation by distance and a high correlation between host anti parasitoid F ST for the same population-pairs was found. At the local level, E. robusta…
Temporal genetic structure in a poecilogonous polychaete: the interplay of developmental mode and environmental stochasticity
2014
Background: Temporal variation in the genetic structure of populations can be caused by multiple factors, including natural selection, stochastic environmental variation, migration, or genetic drift. In benthic marine species, the developmental mode of larvae may indicate a possibility for temporal genetic variation: species with dispersive planktonic larvae are expected to be more likely to show temporal genetic variation than species with benthic or brooded non-dispersive larvae, due to differences in larval mortality and dispersal ability. We examined temporal genetic structure in populations of Pygospio elegans, a poecilogonous polychaete with within-species variation in developmental m…
Stable polymorphism for mutant eye colour geues in populations of Drosophila melanogaster in two different media
1988
In previous work analyzing variability of eye colour alleles existing in natural populations of D. melanogaster, it was observed that the number of females heterozygous for some eye colour alleles was greater in a wine cellar population than in populations outside this cellar. In order to determine which mechanisms caused these eye colour alleles to be favored in the heterozygotes, the changes in the frequency of four eye colour alleles frequently seen in the cellar population (se77o, sf77m, cd77o and multichromosomal 77o) was studied in artificial populations. Two different culture media, one supplemented with 10% ethanol and the other without ethanol were used. It was found that each of t…
Stepping up to genome scan allows stock differentiation in the worldwide distributed blue shark Prionace glauca
2023
The blue shark Prionace glauca is a top predator with one of the widest geographic distributions of any shark species, yet classified as critically endangered in the Mediterranean Sea, and Near Threatened globally. Previous genetic studies did not reject the null hypothesis of a single global population across the worldwide species range. Blue shark situation was proposed as a possible archetype of the ‘grey zone of population differentiation’, coined to designate cases where population structure may be too recent or too faint to be detected using a limited set of markers. Here, blue shark samples collected throughout its global range were sequenced using a specific ddRAD method (DArTseq; G…
Bayesian estimation of partial population continuity using ancient DNA and spatially explicit simulations.
2017
Abstract The retrieval of ancient DNA from osteological material provides direct evidence of human genetic diversity in the past. Ancient DNA samples are often used to investigate whether there was population continuity in the settlement history of an area. Methods based on the serial coalescent algorithm have been developed to test whether the population continuity hypothesis can be statistically rejected by analysing DNA samples from the same region but of different ages. Rejection of this hypothesis is indicative of a large genetic shift, possibly due to immigration occurring between two sampling times. However, this approach is only able to reject a model of full continuity model (a tot…