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PubMed2005

Nonequilibrium conditions following landscape rearrangement: the relative contribution of past and current hydrological landscapes on the genetic structure of a stream-dwelling fish.

Interpreting patterns of population structure in nature is often challenging, especially in dynamic landscapes where population genetic connectivity evolves over time. In this study, we document the absence of migration-drift equilibrium in a stream-dwelling euryhaline fish resulting from past fine-scale drainage rearrangements and evaluate the relative contribution of past and current hydrological landscapes on observed population structure. Based on allelic variation at nine microsatellite loci, genetic relationships among 12 populations of brook charr, Salvelinus fontinalis, from Gros Morne National Park of Canada (GMNP, Newfoundland, Canada) did not reflect current stream hierarchical structure. In addition, we observed no correlation between population differentiation and contemporary landscape features (waterway distance and sums of altitudinal differences). Instead, population relationships were consistent with historical hydrological structure predicted a priori based on geomorphological and biogeographical evidences. Also, population differentiation was strongly correlated with inferred historical landscape features. Contemporary barriers have apparently preserved the signature of past genetic connectivity by constraining gene flow. Based on the relationships between population differentiation and current and past landscape features at various spatial scales, we suggest that brook charr genetic diversity in GMNP is mostly the result of small distance migrations at the time of colonization and subsequent differentiation through drift. This study highlights the potential of approaching landscapes from a combination of contemporary and historical perspectives when interpreting nonequilibrium population structures resulting from landscape rearrangement.

Animals↗
PubMed2001

Population genetic structure of the cleistogamous plant species Viola pubescens Aiton (Violaceae), as indicated by allozyme and ISSR molecular markers.

Few studies of genetic variation have focused on species that reproduce through both showy, chasmogamous (CH) flowers and self-pollinated, cleistogamous (CL) flowers. Using two different techniques, genetic variation was measured in six populations of Viola pubescens Aiton, a yellow-flowered violet found in the temperate forests of eastern North America. Results from eight allozyme loci showed that there was considerable genetic variation in the species, and population structuring was indicated by the presence of unique alleles and a theta (F(ST)) value of 0.29. High genetic variation was also found using ISSR (inter-simple sequence repeat) markers, and population structuring was again evident with unique bands. Viola pubescens appears to have a true mixed-mating system in which selfing through CL and CH flowers contributes to population differentiation, and outcrossing through CH flowers increases genetic variation and gene flow among populations. Overall, allozyme and ISSR techniques yielded similar results, indicating that ISSR markers show potential for use in population genetic studies.

Alleles↗
PubMedDate not supplied

Genetic structure of Triatoma sordida (Hemiptera: Reduviidae) domestic populations from Bolivia: application on control interventions.

The genetic population of Triatoma sordida group 1, a secondary vector of Chagas disease in Bolivia, was studied by multi-locus enzyme electrophoresis. A total of 253 nymphal and adult specimens collected from seven neighbouring localities in the Velasco Province, Department of Santa Cruz, were processed. The relatively low genetic variability was confirmed for this species (rate of polymorphism: 0.20). The absence of genetic disequilibrium detected within the seven localities was demonstrated. A geographical structuration appears between localities with distances greater than 20 km apart. Although T. sordida presents a relatively reduced dispersive capacity, its panmictic unit is wider than compared with T. infestans. Genetic distances between T. sordida populations were correlated with geographic distance. Gene flow between geographic populations of T. sordida provides an efficient framework for effective vigilance and control protocols.

Animals↗
PubMed1990

Mitochondrial DNA variation and genetic structure in Old-World populations of Drosophila subobscura.

To discover the relation between mitochondrial DNA (mtDNA) polymorphism and the geographic population structure of Drosophila subobscura previously established for other genetic traits, a wide Paleartic survey was carried out. A total of 24 nucleomorphs was observed among 261 isofemale lines assayed by 11 restriction endonucleases with 38 different sites in the mtDNA cleavage map. The differentiation of the Canary Islands populations (delta = 0.0119) compared with the mean among all the other continental and insular populations (delta = 0.0002) is striking. Both the great divergence among Canary Islands nucleomorphs (delta = 0.021) compared with the maximum nucleomorph distance in all other populations (delta = 0.017) and the abundance of endemic nucleomorphs (11) on the Canary Islands (50% of the total number of different nucleomorphs found in the entire distribution area) suggest that this molecular differentiation most probably results from the very old age of the Canary Islands populations rather than from drift and founder effects.

Animals↗
PubMed1991

[Frequency criterion of choice of surname for the study of the genetic structure of the population].

On the example of 7 populations of the regional level allowability of using surnames with frequencies exceeding 0.001 in adequate estimation of the population structure indices is shown. The correlation coefficient between genetical distances calculated with the help of all surnames in the list, and those estimated using only frequent surnames was more than 0.9 in all populations studied, values of the correlation coefficient analogous to the FST statistics of Wright being 0.76 to 0.97.

Family↗
PubMed2001

Population genetic structure and vocal dialects in an amazon parrot.

The relationship between cultural and genetic evolution was examined in the yellow-naped amazon Amazona auropalliata. This species has previously been shown to have regional dialects defined by large shifts in the acoustic structure of its learned contact call. Mitochondrial DNA sequence variation from a 680 base pair segment of the first domain of the control region was assayed in 41 samples collected from two neighbouring dialects in Costa Rica. The relationship of genetic variation to vocal variation was examined using haplotype analysis, genetic distance analysis, a maximum-likelihood estimator of migration rates and phylogenetic reconstructions. All analyses indicated a high degree of gene flow and, thus, individual dispersal across dialect boundaries. Calls sampled from sound libraries suggested that temporally stable contact call dialects occur throughout the range of the yellow-naped amazon, while the presence of similar dialects in the sister species Amazona ochrocephala suggests that the propensity to form dialects is ancestral in this clade. These results indicate that genes and culture are not closely associated in the yellow-naped amazon. Rather, they suggest that regional diversity in vocalizations is maintained by selective pressures that promote social learning and allow individual repertoires to conform to local call types.

Animals↗
PubMed2004

Genetic structure of seventy cocoyam (Xanthosoma sagittifolium, Linn, Schott) accessions in Ghana based on RAPD.

Seventy cocoyam accessions collected from the eastern and Volta regions of Ghana were studied using RAPD technique. Ten primers were used to study the genetic diversity and structure of the experimental material and a total of 120 different bands were detected. Levels of polymorphic fragments detected by the ten primers ranged from 69.2% to 100%. In the accessions from the eastern region, the mean observed and effective number of alleles per individual per population and mean Nei's gene diversity were 1.99+/-0.01, 1.53+/-0.12 and 0.312+/-0.05, respectively. Mean observed and effective number of alleles per individual per population and Nei's gene diversity were 1.76+/-0.17, 1.44+/-0.16 and 0.264+/-0.08, respectively for the accessions from the Volta region. Considering the entire collections, the mean observed and effective number of alleles per individual per population and Nei's gene diversity for primers were 1.99+/-0.02, 1.54+/-0.12 and 0.319+/-0.05, respectively. In terms of Nei's F-statistics in the subdivided populations for all primers, the overall gene diversity (Ht) ranged from 0.230 to 0.396 with a mean of 0.313+0.06, within sample gene diversity (Hs) ranged from 0.214 to 0.372 with a mean of 0.286+0.06, gene differentiation (Gst) ranged between 0.005 and 0.178 with a mean of 0.086. Geneflow estimate ranged between 2.309 and 99.500 with a mean of 5.314. The accessions grouped into three main clusters. Accession BD96/183 was the most diverse and may be incorporated into cocoyam breeding programs. The 70 accessions did not cluster into their distinct geographical regions suggesting that there may have been movement of germplasm across the two regions.

DNA Primers↗
PubMed1993

Genetic, structural, and functional studies of a C3-like protein in the marsupial Setonix brachyurus.

A monospecific goat antiserum was prepared against a putative C3 protein (QuC3) from serum of the Western Australian macropod Setonix brachyurus (quokka) using the classical method previously used to produce antiserum against C3 from other mammalian species. Sodium dodecyl sulphate-polyacrylamide gel electrophoretic analysis of reduced immunoprecipitated QuC3 revealed two polypeptide chains with an estimated M(r) of 128,000 and 82,000, respectively--presumably reflecting subunit molecules similar to the C3 alpha and beta subunits found in other mammalian species. No variation in the size of either of the QuC3 alpha or beta subunits was found in different quokka serum samples. Furthermore, no variation in the electrophoretic mobility of QuC3 was detected amongst the same samples using a standard immunofixation electrophoretic technique. The addition of zymosan or immune complexes to fresh quokka serum resulted in activation of QuC3. Immune complex mediated activation of QuC3 was inhibited by the addition of EDTA and Mg(2+)-EGTA. By contrast, EDTA only inhibited activation of QuC3 following incubation of fresh quokka serum with zymosan, suggesting that the quokka has a classical and an alternative C3 activation pathway, similar to those found in eutherian mammals. This study has shown for the first time that one of the macropod marsupials (S. brachyurus) has a C3-like protein with similar structural and functional characteristics to C3 found in eutherian mammals. However, unlike C3 in other mammalian species, genetic variability of the structure of the quokka C3-like protein may be restricted.

Animals↗
PubMed2001

Diversity, genetic structure and evidence of outcrossing in British populations of the rock fern Adiantum capillus-veneris using microsatellites.

Microsatellites were isolated and a marker system was developed in the fern Adiantum capillus-veneris. Polymorphic markers were then used to study the genetic diversity and structure of populations within the UK and Ireland where this species grows at the northern edge of its range, requiring a specific rock habitat and limited to a few scattered populations. Three dinucleotide loci detected a high level of diversity (23 alleles and 28 multilocus genotypes) across the UK and Ireland, with nearly all variation partitioned among rather than within populations. Of 17 populations represented by multiple samples, all except four were monomorphic. Heterozygosity was detected in three populations, all within Glamorgan, Wales (UK), showing evidence of outcrossing. We make inferences on the factors determining the observed levels and patterns of genetic variation and the possible evolutionary history of the populations.

Alleles↗
PubMed1981

The number of genes on the second chromosome of Drosophila melanogaster and a comment on the genetic structure of eukaryotes.

Recessive lethals on the second chromosome were extracted from genetically isolated populations in Australia and the U.K. The frequency of allelism, used in a manner analogous to capture-recapture of animal populations, indicated that the number of genes capable of mutating to lethal had a 95 per cent probability of being in the range 247 to 1140, although excluding possible heterotic and synthetic lethals altered this to 309 to 3568. Possible sources of bias are discussed. The disagreement between these values and those obtained the direct measurements of DNA (more than 10 times greater) is clear. It is suggested that many of the genes of eukaryotes have been duplicated by unequal exchange during recombination and occur in functionally related groups or in supergenes. Some consequences of this hypothesis to population genetics are noted.

Alleles↗
PubMed1992

Remating effects on the genetic structure of female life histories in populations of Drosophila mojavensis.

A quantitative genetic analysis of nine adult fitness components was performed in two populations of cactophilic Drosophila mojavensis under natural conditions of fermenting cactus and ethanol vapour. Female progeny from 18 sires and 36 dams were treated to a range of six exposure periods to males to assess effects of remating frequency on female fitness. Lifetime fecundity increased with increasing male exposure, but longevity showed an intermediate optimum with temporary exposure to males of 2-4 days. Narrow-sense heritabilities were significant for egg production traits while broad-sense heritabilities were significant for longevity-related traits. Positive genetic correlations between components of fitness were expressed among functionally related traits, e.g. longevity was positively correlated with lifetime fecundity, the number of clutches laid, clutch size, and the number of eggs laid per day. Negative genetic correlations were detected between early and late life fecundity suggesting genetic tradeoffs among components of adult fitness.

Animal Nutritional Physiological Phenomena↗
PubMed1998

Population genetic structure in a Robertsonian race of house mice: evidence from microsatellite polymorphism.

Genetic evidence was assessed for inbreeding and population subdivision in a Robertsonian fusion (Rb) race of the western European form of house mouse, Mus musculus domesticus, in central Belgium. Inbreeding, and the factors responsible for subdivision (genetic drift and extinction-recolonization) can theoretically influence the fixation of underdominant Rb variants. The data consisted of allele frequencies of eight microsatellite loci and of the Rb(4.12) and Rb(5.10) chromosomes. Six populations were sampled once, and a seventh was sampled successively over 3 years. No evidence for inbreeding within populations was found. Levels of between-population subdivision were high (theta = 0.15-0.39), and showed no association with either karyotype or geographical distance over 8-60 km. In addition, low values of effective size were found in the successively sampled population (Ne = 5-20). Cases of significant two-locus disequilibria were associated with the most closely linked pair of microsatellite loci (r = 0.15): also consistent with small effective sizes. These results suggest that both the lack of inbreeding, and the combined effects of genetic drift and extinction-recolonization, may promote Rb polymorphism in M. m. domesticus.

Animals↗
PubMed2004

Genetic structure of the purebred domestic dog.

We used molecular markers to study genetic relationships in a diverse collection of 85 domestic dog breeds. Differences among breeds accounted for approximately 30% of genetic variation. Microsatellite genotypes were used to correctly assign 99% of individual dogs to breeds. Phylogenetic analysis separated several breeds with ancient origins from the remaining breeds with modern European origins. We identified four genetic clusters, which predominantly contained breeds with similar geographic origin, morphology, or role in human activities. These results provide a genetic classification of dog breeds and will aid studies of the genetics of phenotypic breed differences.

Algorithms↗
PubMed1995

[Genetic structure and origin of the tetraploid toad Bufo danatensis Pisanetz, 1978 (Amphibia, Bufonidae) of Central Asia. Differentiation of geographic forms and genetic relationship between diploid and tetraploid species].

A hierarchical system, consisting of several levels of genetic divergence, is formed by distribution of genetic distances between diploid taxa of the green toad species complex (subspecies Bufo viridis viridis--B. v. turanensis and species B. viridis--B. sp.) and taxa representing western (B. viridis s.l.) and eastern (B. raddei) Pale-arctic regions. Formally, genetic differentiation of the tetraploid toad B. danatensis from the parapatric diploid species reaches the species level. Genetic diversity of the tetraploid species is more than twofold higher than the total diversity of two modern diploid species. This suggests that B. danatensis was formed with the participation of other unknown species in the past. The polyploid species B. danatensis is assumed to have originated by hybridization of two species groups that arose approximately 2.6 million years ago in Mediterranean and Central Asian regions of the western Palearctic. The genetic heterogeneity of geographical populations of the polyploid species indicates its polyphiletic origin. The heterogeneity range suggests that formation of the tetraploid species continued for a very long period (about 1 million years).

Animals↗
PubMedDate not supplied

[Genetic structure of unisex hybrid population of frogs Rana esculenta complex in lowland Transcarpathian region].

The biochemical genetic marking and analysis of the ploidy and sexual structure of the green frog populations from the Transcarpathian lowlands have demonstrated that this region is inhabited by the unisexual populations composed of the allodiploid females only. Their genome includes a small portion of the marsh frog genic diversity. This phenomenon is discussed in relation to the unisexual population reproduction problem. The assumption is proposed that in the Transcarpathian hybrid populations the hybrids are spawned by the parthenogenesis.

Animals↗
PubMed2000

Spatial and temporal aspects of the genetic structure of Juniperus communis populations.

Juniperus communis is a dioecious, wind pollinated shrub or small tree that produces 'berries' (female cones) containing a small number of seeds that are thought to be dispersed by birds. The expectation, therefore, would be that populations of Juniper are genetically diverse with little structuring between them. In Britain, the species has two main centres of distribution: a highland zone in the north and west, in which populations are still large and sexually reproducing, and a southern zone on chalk downlands in which populations are small and fragmented and individuals suffer from a decline in fertility. Thus, one would expect the large sexually viable populations in the north to exhibit high levels of within-population genetic variation, while the declining southern populations would be genetically depauperate. The analysis of amplified fragment length polymorphisms (AFLPs) was used to test this hypothesis. Surprisingly, all populations studied showed high levels of genetic variation although there was clear structuring between populations. On the basis of the geographical structuring of the populations it was hypothesized that J. communis colonized Britain via three separate routes.

Genetic Markers↗
PubMed1994

Testing a model for the genetic structure of personality: a comparison of the personality systems of Cloninger and Eysenck.

Genetic analysis of data from 2,680 adult Australian twin pairs demonstrated significant genetic contributions to variation in scores on the Harm Avoidance, Novelty Seeking, and Reward Dependence scales of Cloninger's Tridimensional Personality Questionnaire (TPQ), accounting for between 54% and 61% of the stable variation in these traits. Multivariate genetic triangular decomposition models were fitted to determine the extent to which the TPQ assesses the same dimensions of heritable variation as the revised Eysenck Personality Questionnaire. These analyses demonstrated that the personality systems of Eysenck and Cloninger are not simply alternative descriptions of the same dimensions of personality, but rather each provide incomplete descriptions of the structure of heritable personality differences.

Adult↗