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1.
Admixture in Mexico City: implications for admixture mapping of Type 2 diabetes genetic risk factors
Martinez-Marignac VL Valladares A Cameron E Chan A Perera A Globus-Goldberg R Wacher N Kumate J McKeigue P O'Donnell D Shriver MD Cruz M Parra EJ 《Human genetics》2007,120(6):807-819
Admixture mapping is a recently developed method for identifying genetic risk factors involved in complex traits or diseases
showing prevalence differences between major continental groups. Type 2 diabetes (T2D) is at least twice as prevalent in Native
American populations as in populations of European ancestry, so admixture mapping is well suited to study the genetic basis
of this complex disease. We have characterized the admixture proportions in a sample of 286 unrelated T2D patients and 275
controls from Mexico City and we discuss the implications of the results for admixture mapping studies. Admixture proportions
were estimated using 69 autosomal ancestry-informative markers (AIMs). Maternal and paternal contributions were estimated
from geographically informative mtDNA and Y-specific polymorphisms. The average proportions of Native American, European and,
West African admixture were estimated as 65, 30, and 5%, respectively. The contributions of Native American ancestors to maternal
and paternal lineages were estimated as 90 and 40%, respectively. In a logistic model with higher educational status as dependent
variable, the odds ratio for higher educational status associated with an increase from 0 to 1 in European admixture proportions
was 9.4 (95%, credible interval 3.8–22.6). This association of socioeconomic status with individual admixture proportion shows
that genetic stratification in this population is paralleled, and possibly maintained, by socioeconomic stratification. The
effective number of generations back to unadmixed ancestors was 6.7 (95% CI 5.7–8.0), from which we can estimate that genome-wide
admixture mapping will require typing about 1,400 evenly distributed AIMs to localize genes underlying disease risk between
populations of European and Native American ancestry. Sample sizes of about 2,000 cases will be required to detect any locus
that contributes an ancestry risk ratio of at least 1.5. 相似文献
2.
Historical evidence suggests that the Christian Coptic population of Antinoe necropolis, probable descendants of Dynastic
Egyptians, may reflect admixture from Greek and Roman populations. Within the anthropological surveys on Antinoe skeletal
remains (A.D. 300–600), a sample of auditory ossicles was compared with a Dynastic Egyptian sample (“G. Marro” osteological
collection), from Asiut and Gebelen Univariate and multivariate statistical analyses were applied, to this end.
The auditory ossicles are generally larger in the Coptic group; in both groups shape measurements have a high variability,
while size measurements are relatively invariable. Univariate variances are homogeneous but the means are significantly different.
This suggests genetic changes, but identical patterns of variation.
The stepwise discriminant functions analysis and the Generalized Distance, suggesting a biological heterogeneity in the Antinoe
sample in spite of some similarity of the two groups, tend to support this.
Further analyses of the auditory ossicles in Greek and Roman populations are however needed to confirm the gene flow hypothesis
in the Antinoe population, suggested by historical data. 相似文献
3.
J. E. Bernal P. Sarmiento I. Briceno C. Duran S. S. Papiha 《International Journal of Anthropology》1995,10(4):203-208
Blood samples of 1.022 individuals of both sexes, collected during the “Expedicion Humana” programme. Twelve Indian group,
two Negroes, two urban and one mestizo populations of Colombia were C3 typed. The results showed the urban samples have C3*F
genotype frequencies (17 and 20%) similar to the Spanish population. The Negroe system, with lower C3*F gene frequencies (3.5
and 7%) also resembled their parental populations in Africa. The Mestizo population reported in this study showed a lower
value of the C3*F gene (2.2%) than previously studied. suggesting that the degree of admixture may vary in different regions
of the country. As regards the Indian populations, there was a wide range of variation of the C3*F gene (0–19%) many tribes
being monomorphic. This gene may be a marker of recent admixture in Amerindians, but there may be other genetic factors, such
as selection and inbreeding in maintaining high levels of genetic polymorphism in tribes such as Guahibo. 相似文献
4.
Sandra Beleza Joana Campos Jailson Lopes Isabel Inês Araújo Ana Hoppfer Almada António Correia e Silva Esteban J. Parra Jorge Rocha 《PloS one》2012,7(11)
Recently admixed populations offer unique opportunities for studying human history and for elucidating the genetic basis of complex traits that differ in prevalence between human populations. Historical records, classical protein markers, and preliminary genetic data indicate that the Cape Verde islands in West Africa are highly admixed and primarily descended from European males and African females. However, little is known about the variation in admixture levels, admixture dynamics and genetic diversity across the islands, or about the potential of Cape Verde for admixture mapping studies. We have performed a detailed analysis of phenotypic and genetic variation in Cape Verde based on objective skin color measurements, socio-economic status (SES) evaluations and data for 50 autosomal, 34 X-chromosome, and 21 non-recombinant Y-chromosome (NRY) markers in 845 individuals from six islands of the archipelago. We find extensive genetic admixture between European and African ancestral populations (mean West African ancestry = 0.57, sd = 0.08), with individual African ancestry proportions varying considerably among the islands. African ancestry proportions calculated with X and Y-chromosome markers confirm that the pattern of admixture has been sex-biased. The high-resolution NRY-STRs reveal additional patterns of variation among the islands that are most consistent with differentiation after admixture. The differences in the autosomal admixture proportions are clearly evident in the skin color distribution across the islands (Pearson r = 0.54, P-value<2e–16). Despite this strong correlation, there are significant interactions between SES and skin color that are independent of the relationship between skin color and genetic ancestry. The observed distributions of admixture, genetic variation and skin color and the relationship of skin color with SES relate to historical and social events taking place during the settlement history of Cape Verde, and have implications for the design of association studies using this population. 相似文献
5.
Berchemiella wilsonii var. pubipetiolata (Rhamnaceae) is an endangered plant with only four remnant populations in eastern China. Population genetic information is
essential for understanding population history and formulating conservation strategies for this species. Thirteen microsatellite
loci were used to investigate genetic variation and population structure of the four remnant populations. Moderate levels
of expected heterozygosity (H
E = 0.466–0.543) and low allelic diversity (A = 3.1–3.6 and A
R = 2.2–2.4, respectively) were observed within populations. Bottleneck tests found three out of four populations to deviate
from mutation-drift equilibrium under the two-phase model (TPM), suggesting a recent population decline, which is congruent
with known demographic history. The evolutionary history of the species seems dominated by genetic drift rather than gene
flow. Low historical gene flow was inferred from several different approaches and N
m ranged from 0.582 by the private allele method to 0.783 by the coalescent method. Contemporary gene flow was also found to
be even lower for only one first generation migrant was detected with individual-based assignment analysis. Restricted pollen
and seed dispersal as well as a recent decline in population size associated with habitat fragmentation may have contributed
to low levels of historical and contemporary gene flow, and resulted in a high genetic differentiation. Under this scenario,
Berchemiella wilsonii var. pubipetiolata populations are expected to display more pronounced population genetic structure in the future as a result of increased inbreeding
and genetic drift. 相似文献
6.
Liselotte W. Andersen Tina Fredsted Trine Wincentz Cino Pertoldi 《Acta theriologica》2009,54(2):97-110
Denmark lies on the edge of the distributional range of the brown hareLepus europaeus Pallas, 1778, where population differentiation is most likely to occur. A total of 369 brown hares from eight geographically
distinct Danish European brown hare populations were used to study the genetic population structure. In all, 480bp of the
mitochondrial D-loop were sequenced in both directions. Observed genetic diversity (π) was relatively low (π=0.41%) while
haplotype diversity (h=0.808) and the number of unique haplotypes (19) were similar to levels found in other European brown
hare populations. The observed population structure was pronounced (pairwise conventionalF
ST and ϕ
st
ranged between 6.9–57% and 5–69.8%, respectively). There was no correlation between the geographic and the genetic distance.
Population structure was influenced by genetic drift, anthropogenic effects (eg translocation and escapes from hare-farms)
and by post-glacial recolonization from southern refuges or refuges north east of the Black Sea. Analysis of historical population
expansion/fluctuation events indicated that the populations have experienced different demographic events in the recent past.
Relatively high sequence divergence between some populations might be explained by multiple recolonization events after the
last Pleistocene glaciations or by stocking effects. Colonization from southern refuges was supported by the observation that
haplotype 2 in the Danish brown hare was identical to the central European ancestral haplotype c07. 相似文献
7.
Nikoleta Karaiskou Maria Lappa Stefanos Kalomoiris George Oikonomidis Chariklia Psaltopoulou Theodore J. Abatzopoulos Costas Triantaphyllidis Alexander Triantafyllidis 《Conservation Genetics》2011,12(5):1299-1311
The ability to detect genetic differences both in space and time is crucial for conserving genetic variation. It can reveal
genetic diversity and genetic composition changes of declining native populations that are supported through stocking with
captive bred individuals. The present study was designed to analyse the temporal stability of a declining common carp (Cyprinus carpio) population from Lake Volvi (North Greece). Polymorphism was evaluated using seven microsatellite loci at two sampling time
points (separated by 12 years). The genetic variability of four additional populations (from two rivers and two lakes) in
Northern Greece was also investigated for comparison. Heterozygosity values (0.692–0.868) and allelic richness (8.530–11.148)
were high for all studied populations and comparable to other European populations. However, the analysis of temporal common
carp samples from Lake Volvi revealed a significant change in their genetic composition and admixture analysis demonstrated
significant introgression of stocked individuals into the native population. Both temporal and point estimate methods revealed
low effective size (Ne = 61–171.3) for this population, possibly a result of an ancient genetic bottleneck that led to population decline and/or
recent anthropogenic interventions. This low Ne has rendered the native population vulnerable to alteration of its genetic composition. Our study demonstrates that enhancement
programs should be applied cautiously, especially for small populations. Moreover, it underlines the need for temporal analyses,
which may contribute to the evaluation of previous management policies and to future decision making. 相似文献
8.
Juan L. Bouzat 《Genetica》2000,110(2):109-115
A fundamental criterion for recognizing species or populations as potentially endangered is the presence/absence of genetic
diversity. However, the lack of control populations in many studies of natural systems deprives one from unambiguous criteria
for evaluating the genetic effects of small population size and its potential effects on fitness. In this study, I present
an example of how the lack of adequate controls may lead to erroneous conclusions for understanding the role that population
size may play in the preservation of genetic diversity and fitness of natural populations. The genetic analysis of a population
of greater prairie chickens from Illinois, USA, between two time periods (1974–1987 and 1988–1993) in which the studied population
experienced a substantial reduction in size and fitness showed no apparent associations between population size and genetic
diversity. However, genetic analysis of museum specimens from early this century indicated that Illinois prairie chickens
had originally higher levels of genetic diversity, which suggest the Illinois population was already bottlenecked by the 1970s.
This study emphasizes the importance of using historical controls to evaluate the temporal dynamics of genetic variability
in natural populations. The large number of museum collections worldwide may provide a valuable source of genetic information
from past populations, particularly in species currently endangered as a result of human activities.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
The Allee effect can result in a negative population growth rate at low population density. Consequently, populations below
a minimum (critical) density are unlikely to persist. A lower limit on population size should constrain the loss of genetic
variability due to genetic drift during population bottlenecks or founder events. We explored this phenomenon by modeling
changes in genetic variability and differentiation during simulated bottlenecks of the alpine copepod, Hesperodiaptomus shoshone. Lake surveys, whole-lake re-introduction experiments and model calculations all indicate that H. shoshone should be unlikely to establish or persist at densities less than 0.5–5 individuals m−3. We estimated the corresponding range in minimum effective population size using the distribution of habitat (lake) sizes
in nature and used these values to model the expected heterozygosity, allelic richness and genetic differentiation resulting
from population bottlenecks. We found that during realistic bottlenecks or founder events, >90% of H. shoshone populations in the Sierra Nevada may be resistant to significant changes in heterozygosity or genetic distance, and 70–75%
of populations may lose <10% of allelic richness. We suggest that ecological constraints on minimum population size be considered
when using genetic markers to estimate historical population dynamics. 相似文献
10.
Michelle Daya Lize van der Merwe Ushma Galal Marlo M?ller Muneeb Salie Emile R. Chimusa Joshua M. Galanter Paul D. van Helden Brenna M. Henn Chris R. Gignoux Eileen Hoal 《PloS one》2013,8(12)
Admixture is a well known confounder in genetic association studies. If genome-wide data is not available, as would be the case for candidate gene studies, ancestry informative markers (AIMs) are required in order to adjust for admixture. The predominant population group in the Western Cape, South Africa, is the admixed group known as the South African Coloured (SAC). A small set of AIMs that is optimized to distinguish between the five source populations of this population (African San, African non-San, European, South Asian, and East Asian) will enable researchers to cost-effectively reduce false-positive findings resulting from ignoring admixture in genetic association studies of the population. Using genome-wide data to find SNPs with large allele frequency differences between the source populations of the SAC, as quantified by Rosenberg et. al''s -statistic, we developed a panel of AIMs by experimenting with various selection strategies. Subsets of different sizes were evaluated by measuring the correlation between ancestry proportions estimated by each AIM subset with ancestry proportions estimated using genome-wide data. We show that a panel of 96 AIMs can be used to assess ancestry proportions and to adjust for the confounding effect of the complex five-way admixture that occurred in the South African Coloured population. 相似文献
11.
In this study, we report the genetic population structure of the Fire-bellied toad Bombina bombina in Brandenburg (East Germany) in the context of conservation. We analysed 298 samples originating from 11 populations in
Brandenburg using mitochondrial control region sequences and six polymorphic microsatellite loci. For comparison, we included
one population each from Poland and Ukraine into our analysis. Within Brandenburg, we detected a moderate variability in the
mitochondrial control region (19 different haplotypes) and at microsatellite loci (9–12 alleles per locus). These polymorphisms
revealed a clear population structure among toads in Brandenburg, despite a relatively high overall population density and
the moderate size of single populations (100–2000 individuals). The overall genetic population structure is consistent with
a postglacial colonization from South East-Europe and a subsequent population expansion. Based on genetic connectivity, we
infer Management Units (MUs) as targets for conservation. Our genetic survey identified MUs, within which human infrastructure
is currently preventing any genetic exchange. We also detect an unintentional translocation from South East to North West
Brandenburg, presumably in the course of fish stocking activities. Provided suitable conservation measures are taken, Brandenburg
should continue to harbor large populations of this critically endangered species. 相似文献
12.
Senemar S Doroudchi M Pezeshki AM Bazrgar M Torab-Jahromi A Ghaderi A 《Molecular biology reports》2009,36(2):353-356
Iranian population with an Indo-European origin is one of the oldest populations in the world. Historical evidence suggests
the close similarity in the origin of Iranian, European and north Indian population. However, there are few anthropological
and genetic evidences on this subject. This study, which is the first report from Iran, was performed to investigate the genetic
origin of Iranian population using a polymorphism in Cystathionine beta synthase (CBS) gene known as 844INS68bp in this respect,
genomic DNA was extracted from the whole blood of 480 healthy normal blood donors referred to Fars Blood Transfusion Center,
using a salting out method. The fragment containing 844INS68bp was amplified, the normal fragment was 174 bp and the fragment
containing the insertion was 242 bp in length. Results indicated that 418 (87.08%) out of 480 individuals had a normal (N/N)
genotype, 59 (12.29%) individuals were heterozygote (N/I) and 3 (0.63%) had homozygote a mutated genotype (I/I). The total
frequency of 844INS68bp allele was found 6.8% which is similar to with the reported in White Caucasians. Comparison of the
genotype of this study with the polymorphism in other populations revealed that Southern Iranian population has a great similarity
with other Caucasians populations’ especially South Italy and North America while differed from East Asian and African populations.
These results are in agreement with the result of other studied polymorphisms. Therefore, despite the great admixture of Iranian
population with the neighboring non-Caucasian populations during the time, Iranian population still share a genetic background
with other Caucasian populations. 相似文献
13.
Pichler I Mueller JC Stefanov SA De Grandi A Volpato CB Pinggera GK Mayr A Ogriseg M Ploner F Meitinger T Pramstaller PP 《Human biology; an international record of research》2006,78(4):441-464
Most of the inhabitants of South Tyrol in the eastern Italian Alps can be considered isolated populations because of their physical separation by mountain barriers and their sociocultural heritage. We analyzed the genetic structure of South Tyrolean populations using three types of genetic markers: Y-chromosome, mitochondrial DNA (mtDNA), and autosomal Alu markers. Using random samples taken from the populations of Val Venosta, Val Pusteria, Val Isarco, Val Badia, and Val Gardena, we calculated genetic diversity within and among the populations. Microsatellite diversity and unique event polymorphism diversity (on the Y chromosome) were substantially lower in the Ladin-speaking population of Val Badia compared to the neighboring German-speaking populations. In contrast, the genetic diversity of mtDNA haplotypes was lowest for the upper Val Venosta and Val Pusteria. These data suggest a low effective population size, or little admixture, for the gene pool of the Ladin-speaking population from Val Badia. Interestingly, this is more pronounced for Ladin males than for Ladin females. For the pattern of genetic Alu variation, both Ladin samples (Val Gardena and Val Badia) are among the samples with the lowest diversity. An admixture analysis of one German-speaking valley (Val Venosta) indicates a relatively high genetic contribution of Ladin origin. The reduced genetic diversity and a high genetic differentiation in the Rhaetoroman- and German-speaking South Tyrolean populations may constitute an important basis for future medical genetic research and gene mapping studies in South Tyrol. 相似文献
14.
The genetic structure of mangrove species is greatly affected by their geographic history. Nine natural populations of Ceriops tagal were collected from Borneo, the Malay Peninsula, and India for this phylogeographic study. Completely different haplotype
compositions on the east versus west coasts of the Malay Peninsula were revealed using the atpB-rbcL and trnL-trnF spacers of chloroplast DNA. The average haplotype diversity (Hd) of the total population was 0.549, nucleotide diversity
(θ) was 0.030, and nucleotide difference (π) was 0.0074. The cladogram constructed by the index of population differentiation
(G
ST) clearly separated the South China Sea populations from the Indian Ocean populations. In the analysis of the minimum spanning
network, the Indian Ocean haplotypes were all derived from South China Sea haplotypes, suggesting a dispersal route of C. tagal from Southeast Asia to South Asia. The Sunda Land river system and surface currents might be accountable for the gene flow
directions in the South China Sea and Bay of Bengal, respectively. The historical geography not only affected the present
genotype distribution but also the evolution of C. tagal. These processes result in the genetic differentiation and the differentiated populations that should be considered as Management
Units (MUs) for conservation measurements instead of random forestation, which might lead to gene mixing and reduction of
genetic variability of mangrove species. According to this phylogeographic study, populations in Borneo, and east and west
Malay Peninsula that have unique genotypes should be considered as distinct MUs, and any activities resulting in gene mixing
with each other ought to be prevented. 相似文献
15.
O. Rickards 《Human Evolution》1995,10(1):5-16
Data on the frequency of the mtDNA region V deletion were used to estimate the relative maternal contribution from the parental
populations to the gene pools of the two Black communities of Rio Cayapas and Viche in northern Ecuador. Ethnohistorical records
and nuclear DNA data indicate that these populations are hybrids of West African and Amerindian populations. The unique distribution
of the DNA marker in these parental groups provided good admixture estimates. The fraction of mtDNA of Amerindian origin in
the population of Rio Cayapas is quite small (8%±5%), whereas in the community of Viche the native Americans contributed the
major portion of the gene pool (51%±15). The mtDNA estimate for Rio Cayapas is similar to that of some protein polymorphisms,
which confirms the cultural and genetic isolation of this community from the neighboring native population. On the other hand,
the admixture value obtained from nuclear genes in Viche is statistically different from the estimate obtained from mtDNA
data. This supports the traditional belief, gathered from historical records and cultural data, that the contribution from
Indian females was higher than that of Indian males, at least in the primary settlements of the African-American population
of Esmeraldas. 相似文献
16.
Brad L. Smith Ching-Ping Lu Blanca García-Cortés Jordi Vi?as Shean-Ya Yeh Jaime R. Alvarado Bremer 《PloS one》2015,10(6)
Previous genetic studies of Atlantic swordfish (Xiphias gladius L.) revealed significant differentiation among Mediterranean, North Atlantic and South Atlantic populations using both mitochondrial and nuclear DNA data. However, limitations in geographic sampling coverage, and the use of single loci, precluded an accurate placement of boundaries and of estimates of admixture. In this study, we present multilocus analyses of 26 single nucleotide polymorphisms (SNPs) within 10 nuclear genes to estimate population differentiation and admixture based on the characterization of 774 individuals representing North Atlantic, South Atlantic, and Mediterranean swordfish populations. Pairwise F
ST values, AMOVA, PCoA, and Bayesian individual assignments support the differentiation of swordfish inhabiting these three basins, but not the current placement of the boundaries that separate them. Specifically, the range of the South Atlantic population extends beyond 5°N management boundary to 20°N-25°N from 45°W. Likewise the Mediterranean population extends beyond the current management boundary at the Strait of Gibraltar to approximately 10°W. Further, admixture zones, characterized by asymmetric contributions of adjacent populations within samples, are confined to the Northeast Atlantic. While South Atlantic and Mediterranean migrants were identified within these Northeast Atlantic admixture zones no North Atlantic migrants were identified respectively in these two neighboring basins. Owing to both, the characterization of larger number of loci and a more ample spatial sampling coverage, it was possible to provide a finer resolution of the boundaries separating Atlantic swordfish populations than previous studies. Finally, the patterns of population structure and admixture are discussed in the light of the reproductive biology, the known patterns of dispersal, and oceanographic features that may act as barriers to gene flow to Atlantic swordfish. 相似文献
17.
Bazrgar M Karimi M Fathzadeh M Senemar S Peiravian F Shojaee A Saadat M 《Molecular biology reports》2008,35(4):495-499
Background: Apolipoprotein E (apoE) with three major alleles E2, E3 and E4 is one of the critical genes in lipid metabolism. Common
apoE alleles are in association with an increase in risk for central nervous and cardiovascular diseases such as Alzheimer’s
disease, dementia, multiple sclerosis, atherosclerosis, coronary heart disease, hyperlipoproteinemia and stroke. ApoE3 is
known as the most frequent allele in all populations, while association of apoE gene polymorphism with reported diseases have
mostly been related to other two major alleles especially apoE4. Objective: To determine of apoE alleles frequencies in Southern Iran and comparison of those frequencies with other populations. Methods: DNA was extracted from the whole blood of 198 healthy unrelated candidates from population of Fars Province, Southern Iran,
for apoE genotyping who were checked up by a physician. The frequencies of apoE alleles were compared with other populations
by χ2 test. Results: The frequencies of E2, E3 and E4 were 0.063, 0.886 and 0.051 respectively. These values were similar to those reported from
populations of Kuwait, Oman, Lebanon, India, Turkey, Greece, Spain, Sardinia Islands of Italy and two Iranian populations
but were different from South of Italy and Caucasians in other Europe regions, American, American-Indian, African, East Asian
and Saudi populations (P < 0.05). Conclusion: The frequency of E4 allele as a genetic risk factor for some multifactorial diseases in the population of Southern Iran
is in the lowest reported amounts in the world. Iranian population has Caucasoid origin but differs from some Caucasian populations
in Europe and America. The results of present study are in agreement with the historical evidences which show admixture of
Iranian population with other populations and some studies based on genetic polymorphisms in the population of Southern Iran. 相似文献
18.
Pereira L Prata MJ Brión M Jobling MA Carracedo A Amorim A 《Human biology; an international record of research》2000,72(6):937-944
The potential of Y-chromosome biallelic marker haplotypes to infer population affiliations and structures was exploited to analyze four populations from the southwestern edge of Europe, namely north, central, and south Portugal and Galicia. Three markers subdividing the YAP+ lineage were analyzed: the YAP Alu element insertion itself and the SRY8299 and sY81 base substitutions; these respectively define three haplotypes known as 4, 21, and 8. Only haplotype 21 was detected presenting an increasing north-to-south frequency gradient, from 9.6% (Galicia) to 24.5% (South Portugal). This clinal distribution most likely reflects the genetic input associated with the Neolithic spread of agriculture, but we cannot exclude other movements as potential contributors to the distribution. In this context, it is interesting to note the consistency between the clinal variation and the population movement associated with Islamic rule in Iberia. The absence of haplotype 8, a marker of sub-Saharan populations, suggests that, despite the massive introductions of African slaves in historical times, there was little admixture between the African males and Western Iberian populations. 相似文献
19.
Sixty years of anthropogenic pressure: a spatio-temporal genetic analysis of brown trout populations subject to stocking and population declines 总被引:1,自引:1,他引:0
MICHAEL M. HANSEN DYLAN J. FRASER† KRISTIAN MEIER KAREN-LISE D. MENSBERG 《Molecular ecology》2009,18(12):2549-2562
Analyses of historical samples can provide invaluable information on changes to the genetic composition of natural populations resulting from human activities. Here, we analyse 21 microsatellite loci in historical (archived scales from 1927 to 1956) and contemporary samples of brown trout ( Salmo trutta ) from six neighbouring rivers in Denmark, to compare the genetic structure of wild populations before and after population declines and stocking with nonlocal strains of hatchery trout. We show that all populations have been strongly affected by stocking, with admixture proportions ranging from 14 to 64%. Historical population genetic structure was characterized by isolation by distance and by positive correlations between historical effective population sizes and habitat area within river systems. Contemporary population genetic structure still showed isolation by distance, but also reflected differences among populations in hatchery trout admixture proportions. Despite significant changes to the genetic composition within populations over time, dispersal rates among populations were roughly similar before and after stocking. We also assessed whether population declines or introgression by hatchery strain trout should be the most significant conservation concern in this system. Based on theoretical considerations, we argue that population declines have had limited negative effects for the persistence of adaptive variation, but admixture with hatchery trout may have resulted in reduced local adaptation. Collectively, our study demonstrates the usefulness of analysing historical samples for identifying the most important consequences of human activities on the genetic structure of wild populations. 相似文献
20.
Juan C. Marin Benito A. González Elie Poulin Ciara S. Casey Warren E. Johnson 《Molecular ecology》2013,22(2):463-482
A comprehensive study of the phylogeography and population genetics of the largest wild artiodactyl in the arid and cold‐temperate South American environments, the guanaco (Lama guanicoe) was conducted. Patterns of molecular genetic structure were described using 514 bp of mtDNA sequence and 14 biparentally inherited microsatellite markers from 314 samples. These individuals originated from 17 localities throughout the current distribution across Peru, Bolivia, Argentina and Chile. This confirmed well‐defined genetic differentiation and subspecies designation of populations geographically separated to the northwest (L. g. cacsilensis) and southeast (L. g. guanicoe) of the central Andes plateau. However, these populations are not completely isolated, as shown by admixture prevalent throughout a limited contact zone, and a strong signal of expansion from north to south in the beginning of the Holocene. Microsatellite analyses differentiated three northwestern and 4–5 southeastern populations, suggesting patterns of genetic contact among these populations. Possible genetic refuges were identified, as were source‐sink patterns of gene flow at historical and recent time scales. Conservation and management of guanaco should be implemented with an understanding of these local population dynamics while also considering the preservation of broader adaptive variation and evolutionary processes. 相似文献