Search results for "Genetic Variation"
showing 10 items of 836 documents
Detection of ephemeral genetic sub-structure in the narrow endemic Abies nebrodensis (Lojac.) Mattei (Pinaceae) using RAPD markers
2004
A. nebrodensis (Nebrodi fir, Sicilian fir) is restricted to a small area of the Madonie Natural Park in Sicily. According to recent estimates, its only population consists of 30 adult individuals and a fluctuating number of juveniles derived from natural regeneration; besides, some hundreds of cultivated plants are preserved as ex situ collection. We used RAPD data from six 10-mer primers to examine the consequences of extensive historical clearance and human pressures on the extant population. Data from multiple life stages and different habitat conditions were considered, affording an opportunity to ascertain for the first time the structure of genetic variation in the extant uneven-aged …
Genetic population structure of two cryptic Gammarus fossarum types across a contact zone
1998
Previous studies have revealed inconsistent results about the taxonomic status of European Gammarus fossarum forms. The variability in morphology and hybridization ability has not shown clear geographic patterns, whereas on a genetical basis two Central European G. fossarum forms have been proposed. In the present study the genetic structure of G. fossarum populations was investigated across a natural contact zone. For the first time direct comparisons of allotopic versus syntopic populations were feasible. 24 Populations of G. fossarum plus 4 populations of G. pulex (as outgroup) were sampled along 2 transects across the contact zone. The genotypes of about 60 individuals per population we…
Genetic differentiation of three species of Matthiola (Brassicaceae) in the Sicilian insular system
2005
We examined the genetic variation of 12 isozyme loci in 14 populations of Matthiola (Brassicaceae) representing the geographic distribution of the species M. incana, M. fruticulosa ssp. fruticulosa and M. tricuspidata in the Sicilian insular system and the adjacent mainland areas to estimate the levels and apportionment of genetic variation in the insular populations and to understand their population dynamics. The disparity in the distribution of polymorphism in populations of M. incana ssp. incana (low within populations but with high values of F ST and G ST ) contrasts with the homogeneity in the inter-population distribution of the high genetic variation detected in M. tricuspidata and …
Diabetes: Genetic variation underpins metformin response.
2016
Metformin is the first-line antidiabetic drug with over 100 million users worldwide, yet its mechanism of action remains unclear1. Here the Metformin Genetics (MetGen) Consortium reports a three-stage genome-wide association study (GWAS), consisting of 13,123 participants of different ancestries. The C allele of rs8192675 in the intron of SLC2A2, which encodes the facilitated glucose transporter GLUT2, was associated with a 0.17% (p=6.6×10−14) greater metformin-induced in haemoglobin A1c (HbA1c) in 10,577 participants of European ancestry. rs8192675 is the top cis expression quantitative trait locus (cis-eQTL) for SLC2A2 in 1,226 human liver samples, suggesting a key role for hepatic GLUT2 …
Tras la pista del VIH: los estudios evolutivos y la comprensión del sida.
2013
El VIH o virus de la inmunodeficiencia humana tiene un gran impacto sanitario, social y económico; las terapias actuales permiten controlar la infección pero no se ha encontrado tratamiento curativo ni vacuna efectiva. Para conseguir estos objetivos, debe tenerse en cuenta la gran variabilidad genética y rápida evolución del VIH, asociadas, por ejemplo, a la aparición de variantes de resistencia a fármacos o de cambios antigénicos.
Molecular phylogeny and ultrastructure of the lichen microalga Asterochloris mediterranea sp. nov. from Mediterranean and Canary Islands ecosystems
2015
The microalgae of the genus Asterochloris are the preferential phycobionts in Cladonia, Lepraria and Stereocaulon lichens. Recent studies have highlighted the hidden diversity of the genus, even though phycobionts hosting Cladonia spp. in Mediterranean and Canarian ecosystems have been poorly explored. Phylogenetic analyses were made by concatenation of the sequences obtained with a plastid -LSU rDNA- and two nuclear -ITS rDNA and actin- molecular markers of the phycobionts living in several populations of Cladonia convoluta-C. foliacea complex, C. rangiformis and C. cervicornis species widely distributed in these areas in a great variety of substrata and habitats. A new strongly supported …
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…
Adaptation to a seasonally varying environment: a strong latitudinal cline in reproductive diapause combined with high gene flow in Drosophila montan…
2011
Adaptation to seasonal changes in the northern hemisphere includes an ability to predict the forthcoming cold season from gradual changes in environmental cues early enough to prepare for the harsh winter conditions. The magnitude and speed of changes in these cues vary between the latitudes, which induces strong selection pressures for local adaptation. We studied adaptation to seasonal changes in Drosophila montana, a northern maltfly, by defining the photoperiodic conditions leading to adult reproductive diapause along a latitudinal cline in Finland and by measuring genetic differentiation and the amount of gene flow between the sampling sites with microsatellites. Our data revealed a cl…
Evolution in Space and Time: The Second Synthesis between Ecology, Evolutionary Biology, and the Philosophy of Biology
2023
Es un hecho sorprendente que para la mayor parte de la biología evolutiva, rara vez hemos estudiado cómo se desarrolla típicamente la evolución en la naturaleza, en ambientes ecológicos cambiantes, en el espacio y el tiempo. Si bien la ecología desempeñó un papel importante en la eventual aceptación del punto de vista de la evolución genética de poblaciones en la síntesis moderna (alrededor de 1918-1950), desempeñó un papel menor en el desarrollo de la teoría evolutiva hasta la década de 1980, cuando comenzamos a estudiar sistemáticamente la teoría de la evolución. dinámica evolutiva de las poblaciones naturales en el espacio y el tiempo. Como resultado, la teoría evolutiva se construyó ini…
Microbial succession of nitrate-reducing bacteria in the rhizosphere of Poa alpina across a glacier foreland in the Central Alps
2006
International audience; Changes in community structure and activity of the dissimilatory nitrate-reducing community were investigated across a glacier foreland in the Central Alps to gain insight into the successional pattern of this functional group and the driving environmental factors. Bulk soil and rhizosphere soil of Poa alpina was sampled in five replicates in August during the flowering stage and in September after the first snowfalls along a gradient from 25 to 129 years after deglaciation and at a reference site outside the glacier foreland (> 2000 years deglaciated). In a laboratory-based assay, nitrate reductase activity was determined colorimetrically after 24 h of anaerobic inc…