Search results for "GENETIC VARIABILITY"
showing 10 items of 200 documents
Differences in allozyme patterns between Diaphanosoma brachyurum and Diaphanosoma mongolianum, as revealed in Central European populations
1995
Recent taxonomic revisions in the genus Diaphanosoma have made the uncertainty in species discrimination with morphological characters obvious. Therefore species characterization on a genetic basis seems to be required. Here we examined the genetic structure of two Diaphanosoma mongolianum populations and three Diaphanosoma brachyurum populations in Central Europe by allozyme electrophoresis. A genetic differentiation between both species was evident. 5 out of 9 tested loci carried diagnostic alleles. Both species differed in their habitat choice: D. mongolianum was adapted to higher trophic levels than D. brachyurum. Co-occurrence was observed in a eutrophic lake. Populations sampled from …
Selection and long-term cultures of high-yielding Digitalis obscura plants: RAPD markers for analysis of genetic stability
1996
Fifteen wild-growing plants of Digitalis obscura collected in three differents regions were characterized according to their capacities to biosynthesize cardenolides and to proliferate in vitro. Great genotype-dependent variabilities were found in both parameters. Selected genotypes were differentiated using randomly amplified polymorphic DNA (RAPD) markers. Once an elite genotype with high-yielding properties was isolated and micropropagated during 2 years, identity of the donor plant and the regenerants was confirmed by RAPD analysis.
The effect of periodic bottlenecks on the competitive ability of Drosophila pseudoobscura lines.
1993
Competition experiments between several Drosophila pseudoobscura strains that were previously subjected to periodic bottlenecks of different sizes and D. willistoni have been carried out. Contrary to previous results with these two species, where stable coexistence was detected, populations of D. pseudoobscura displaced D. willistoni in a few generations. By using a relative fitness measure, the control lines (that had not gone through bottlenecks) outcompeted D. willistoni faster than bottlenecked lines. One of these, corresponding to the minimum possible bottleneck size of one pair, also shows significantly lower relative fitness than the other strains. These results are discussed in rela…
Demographic characterization and genetic variability of the Girgentana goat breed by the analysis of genealogical data
2004
The aim of this paper is to present an overview of the actual Sicilian Girgentana population structure by the analysis ofgenealogical data. Statistics show that in 1983 the population consisted of 30,000 Girgentana goats; ten years lateralmost 98% of the entire Girgentana population disappeared. The remaining population consists of 461 individuals (134males and 327 females), with 368 living animals. The effective population size is 380 individuals. The inbreeding rate pergeneration was equal to 0.13%. The average estimated inbreeding level within the living male population was equal to0.8% (0-15%); and the average inbreeding level within the living female population was equal to 0.7% (0-31%…
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…
The voyage of an invasive species across continents: genetic diversity of North American and European Colorado potato beetle populations
2005
The paradox of successful invading species is that they are likely to be genetically depauperate compared to their source population. This study on Colorado potato beetles is one of the few studies of the genetic consequences of continent-scale invasion in an insect pest. Understanding gene flow, population structure and the potential for rapid evolution in native and invasive populations offers insights both into the dynamics of small populations that become successful invaders and for their management as pests. We used this approach to investigate the invasion of the Colorado potato beetle (Leptinotarsa decemlineata) from North America to Europe. The beetles invaded Europe at the beginnin…
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 diversity in theCentaurea cinerariagroup (Compositae) in Sicily using isozymes
2006
Abstract The genetic diversity of seven taxa endemic to Sicily, C. cineraria, C. busambarensis, C. ucriae subsp. ucriae, C. ucriae subsp. umbrosa, C. todari, C. erycina and C. saccensis, from 11 localities was investigated using isozymes. Eight loci from five enzyme systems (IDH, MDH, PGD, PGM and PGI) were examined. A total of 19 alleles were identified, some rare and two of them exclusive to different populations. The allelic frequencies and the genetic variability values for each population were calculated. On the whole, the genetic diversity, i.e., average polymorphism (P) = 0.41, average number of alleles per locus (A) = 1.75, Nei's gene diversity (H) = 0.18, is moderate, with the high…
Analysis of gene flow and habitat patch network for Chazara briseis (Lepidoptera: Satyridae) in an agricultural landscape
1997
Abstract A fine geographic-scale population genetic structure analysis was performed for the endangered butterfly species Chazara briseis in the region of Halle an der Saale, Germany, for the investigation of gene flow and possible effects of habitat fragmentation on genetic variability. Patterns of genetic variance were estimated by allozyme electrophoresis and quantified with F -statistics. Levels of genetic variation were high, expected heterozygosity H e = 0.20, and mean number of alleles per locus, A = 1.93, indicating large population sizes. Butterflies inhabiting the study area probably constituted just one population and the fragmented nature of the habitat patches did not substanti…
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…