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1.
Nat Commun ; 12(1): 3717, 2021 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-34162841

RESUMO

Rawls argued that fairness in human societies can be achieved if decisions about the distribution of societal rewards are made from behind a veil of ignorance, which obscures the personal gains that result. Whether ignorance promotes fairness in animal societies, that is, the distribution of resources to reduce inequality, is unknown. Here we show experimentally that cooperatively breeding banded mongooses, acting from behind a veil of ignorance over kinship, allocate postnatal care in a way that reduces inequality among offspring, in the manner predicted by a Rawlsian model of cooperation. In this society synchronized reproduction leaves adults in a group ignorant of the individual parentage of their communal young. We provisioned half of the mothers in each mongoose group during pregnancy, leaving the other half as matched controls, thus increasing inequality among mothers and increasing the amount of variation in offspring birth weight in communal litters. After birth, fed mothers provided extra care to the offspring of unfed mothers, not their own young, which levelled up initial size inequalities among the offspring and equalized their survival to adulthood. Our findings suggest that a classic idea of moral philosophy also applies to the evolution of cooperation in biological systems.


Assuntos
Comportamento Animal/fisiologia , Herpestidae/fisiologia , Reprodução/fisiologia , Comportamento Social , Animais , Animais Recém-Nascidos , Peso Corporal/fisiologia , Cruzamento , Feminino , Masculino , Modelos Teóricos , Gravidez , Predomínio Social
2.
R Soc Open Sci ; 7(7): 200419, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32874636

RESUMO

Ectomycorrhizal fungi are key players in terrestrial ecosystems yet their mating systems and population dynamics remain poorly understood. We investigated the fine-scale relatedness structure and genetic diversity of Boletus edulis, one of the world's most commercially important wild mushrooms. Microsatellite genotyping of fruiting bodies from 14 different sites around Bielefeld in Germany revealed little in the way of population structure over a geographic scale of several kilometres. However, on a more local scale we found evidence for elevated relatedness as well as inbreeding. We also observed a significant negative association between the genetic diversity of fruit and the age of the trees under which they were sampled. Taken together, our results suggest that as genets mature, they compete and potentially create conditions under which further spores struggle to become established. By implication, even though this species is widely picked, propagules remain common enough to create strong competition when new habitats become available.

3.
J Neonatal Perinatal Med ; 13(1): 5-9, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31594260

RESUMO

BACKGROUND: False negative pulse oximeter results occur in new born infants with critical congenital heart disease who have an oximeter saturation ≥95%. Some of these infants have abnormal physical findings but others do not. OBJECTIVES: To determine the causes of false negative results. METHODS: Mathematical analysis of determinants of arterial oxygen saturation and discussion of oximeter bias. RESULTS: False negative oximeter results are not rare; the sensitivity of pulse oximetry screening for critical congenital heart disease is about 80%. The high saturation may be due to a very small right-to-left shunt at the time of study, a relatively high cardiac output and mixed venous saturation, or to positive bias in oximeter readings. It may also be due to some critical congenital heart lesions that do not show desaturation at the time of testing. CONCLUSIONS: A diagnosis of a normal heart based on a negative oximeter test is presumptive, and requires careful follow-up for 1-2 weeks after birth.


Assuntos
Cardiopatias Congênitas/diagnóstico , Diagnóstico Ausente , Oximetria , Reações Falso-Negativas , Cardiopatias Congênitas/metabolismo , Humanos , Recém-Nascido , Programas de Rastreamento , Oxigênio/metabolismo , Sensibilidade e Especificidade
4.
Nat Commun ; 9(1): 4836, 2018 11 16.
Artigo em Inglês | MEDLINE | ID: mdl-30446730

RESUMO

A central paradigm in conservation biology is that population bottlenecks reduce genetic diversity and population viability. In an era of biodiversity loss and climate change, understanding the determinants and consequences of bottlenecks is therefore an important challenge. However, as most studies focus on single species, the multitude of potential drivers and the consequences of bottlenecks remain elusive. Here, we combined genetic data from over 11,000 individuals of 30 pinniped species with demographic, ecological and life history data to evaluate the consequences of commercial exploitation by 18th and 19th century sealers. We show that around one third of these species exhibit strong signatures of recent population declines. Bottleneck strength is associated with breeding habitat and mating system variation, and together with global abundance explains much of the variation in genetic diversity across species. Overall, bottleneck intensity is unrelated to IUCN status, although the three most heavily bottlenecked species are endangered. Our study reveals an unforeseen interplay between human exploitation, animal biology, demographic declines and genetic diversity.


Assuntos
Caniformia/genética , Variação Genética , Modelos Estatísticos , Animais , Caniformia/classificação , Conservação dos Recursos Naturais , Ecossistema , Técnicas de Genotipagem , História do Século XVIII , História do Século XIX , História do Século XX , História do Século XXI , Humanos , Repetições de Microssatélites , Dinâmica Populacional/história
5.
R Soc Open Sci ; 5(10): 181227, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30473858

RESUMO

Evaluating how populations are connected by migration is important for understanding species resilience because gene flow can facilitate recovery from demographic declines. We therefore investigated the extent to which migration may have contributed to the global recovery of the Antarctic fur seal (Arctocephalus gazella), a circumpolar distributed marine mammal that was brought to the brink of extinction by the sealing industry in the eighteenth and nineteenth centuries. It is widely believed that animals emigrating from South Georgia, where a relict population escaped sealing, contributed to the re-establishment of formerly occupied breeding colonies across the geographical range of the species. To investigate this, we interrogated a genetic polymorphism (S291F) in the melanocortin 1 receptor gene, which is responsible for a cream-coloured phenotype that is relatively abundant at South Georgia and which appears to have recently spread to localities as far afield as Marion Island in the sub-Antarctic Indian Ocean. By sequencing a short region of this gene in 1492 pups from eight breeding colonies, we showed that S291F frequency rapidly declines with increasing geographical distance from South Georgia, consistent with locally restricted gene flow from South Georgia mainly to the South Shetland Islands and Bouvetøya. The S291F allele was not detected farther afield, suggesting that although emigrants from South Georgia may have been locally important, they are unlikely to have played a major role in the recovery of geographically more distant populations.

6.
Cardiovasc J Afr ; 28(5): 279, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29144531
7.
Heredity (Edinb) ; 118(4): 322-329, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-27804964

RESUMO

Understanding selection in the wild remains a major aim of evolutionary ecology and work by Ford and colleagues on the meadow brown butterfly Maniola jurtina did much to ignite this agenda. A great deal of their work was conducted during the 1950s on the Isles of Scilly. They documented island-specific wing-spot patterns that remained consistent over about a decade, but patterns on some islands changed after environmental perturbation. It was suggested that these wing-spot patterns reflected island-specific selection and that there was little migration between islands. However, genetic studies to test the underlying assumption of restricted migration are lacking and it is also unknown whether the originally described wing-spot patterns have persisted over time. We therefore collected female butterflies from five of Ford's original study locations, including three large islands (St Mary's, St Martin's and Tresco) and two small islands (Tean and St Helen's). Wing-spot patterns had not changed appreciably over time on three of the islands (two large and one small), but were significantly different on the other two. Furthermore, analysis of 176 amplified fragment length polymorphisms revealed significant genome-wide differentiation among the five islands. Our findings are consistent with Ford's conclusions that despite the close proximity of these islands, there is restricted gene flow among them.


Assuntos
Borboletas/genética , Genética Populacional , Asas de Animais , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Animais , Evolução Biológica , Feminino , Fluxo Gênico , Ilhas , Modelos Genéticos , Pigmentação/genética , Reino Unido
8.
R Soc Open Sci ; 3(7): 160291, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27493782

RESUMO

Understanding the causes of population decline is crucial for conservation management. We therefore used genetic analysis both to provide baseline data on population structure and to evaluate hypotheses for the catastrophic decline of the South American sea lion (Otaria flavescens) at the Falkland Islands (Malvinas) in the South Atlantic. We genotyped 259 animals from 23 colonies across the Falklands at 281 bp of the mitochondrial hypervariable region and 22 microsatellites. A weak signature of population structure was detected, genetic diversity was moderately high in comparison with other pinniped species, and no evidence was found for the decline being associated with a strong demographic bottleneck. By combining our mitochondrial data with published sequences from Argentina, Brazil, Chile and Peru, we also uncovered strong maternally directed population structure across the geographical range of the species. In particular, very few shared haplotypes were found between the Falklands and South America, and this was reflected in correspondingly low migration rate estimates. These findings do not support the prominent hypothesis that the decline was caused by migration to Argentina, where large-scale commercial harvesting operations claimed over half a million animals. Thus, our study not only provides baseline data for conservation management but also reveals the potential for genetic studies to shed light upon long-standing questions pertaining to the history and fate of natural populations.

9.
Heredity (Edinb) ; 117(4): 290-9, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27553455

RESUMO

Long-term genetic data from intensively monitored natural populations are important for understanding how effective population sizes (Ne) can vary over time. We therefore genotyped 1622 common buzzard (Buteo buteo) chicks sampled over 12 consecutive years (2002-2013 inclusive) at 15 microsatellite loci. This data set allowed us to both compare single-sample with temporal approaches and explore temporal patterns in the effective number of parents that produced each cohort in relation to the observed population dynamics. We found reasonable consistency between linkage disequilibrium-based single-sample and temporal estimators, particularly during the latter half of the study, but no clear relationship between annual Ne estimates () and census sizes. We also documented a 14-fold increase in between 2008 and 2011, a period during which the census size doubled, probably reflecting a combination of higher adult survival and immigration from further afield. Our study thus reveals appreciable temporal heterogeneity in the effective population size of a natural vertebrate population, confirms the need for long-term studies and cautions against drawing conclusions from a single sample.


Assuntos
Falconiformes/genética , Genética Populacional/métodos , Densidade Demográfica , Animais , Genótipo , Alemanha , Desequilíbrio de Ligação , Repetições de Microssatélites , Modelos Genéticos , Dinâmica Populacional
10.
Mol Ecol Resour ; 16(4): 909-21, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26683564

RESUMO

Custom genotyping arrays provide a flexible and accurate means of genotyping single nucleotide polymorphisms (SNPs) in a large number of individuals of essentially any organism. However, validation rates, defined as the proportion of putative SNPs that are verified to be polymorphic in a population, are often very low. A number of potential causes of assay failure have been identified, but none have been explored systematically. In particular, as SNPs are often developed from transcriptomes, parameters relating to the genomic context are rarely taken into account. Here, we assembled a draft Antarctic fur seal (Arctocephalus gazella) genome (assembly size: 2.41 Gb; scaffold/contig N50 : 3.1 Mb/27.5 kb). We then used this resource to map the probe sequences of 144 putative SNPs genotyped in 480 individuals. The number of probe-to-genome mappings and alignment length together explained almost a third of the variation in validation success, indicating that sequence uniqueness and proximity to intron-exon boundaries play an important role. The same pattern was found after mapping the probe sequences to the Walrus and Weddell seal genomes, suggesting that the genomes of species divergent by as much as 23 million years can hold information relevant to SNP validation outcomes. Additionally, reanalysis of genotyping data from seven previous studies found the same two variables to be significantly associated with SNP validation success across a variety of taxa. Finally, our study reveals considerable scope for validation rates to be improved, either by simply filtering for SNPs whose flanking sequences align uniquely and completely to a reference genome, or through predictive modelling.


Assuntos
Erros de Diagnóstico , Otárias/classificação , Otárias/genética , Genética Populacional/métodos , Genoma , Técnicas de Genotipagem/métodos , Polimorfismo de Nucleotídeo Único , Animais , Análise de Sequência de DNA , Estudos de Validação como Assunto
11.
Biol Lett ; 10(12): 20140898, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25540153

RESUMO

As breeding between relatives often results in inbreeding depression, inbreeding avoidance is widespread in the animal kingdom. However, inbreeding avoidance may entail fitness costs. For example, dispersal away from relatives may reduce survival. How these conflicting selection pressures are resolved is challenging to investigate, but theoretical models predict that inbreeding should occur frequently in some systems. Despite this, few studies have found evidence of regular incest in mammals, even in social species where relatives are spatio-temporally clustered and opportunities for inbreeding frequently arise. We used genetic parentage assignments together with relatedness data to quantify inbreeding rates in a wild population of banded mongooses, a cooperatively breeding carnivore. We show that females regularly conceive to close relatives, including fathers and brothers. We suggest that the costs of inbreeding avoidance may sometimes outweigh the benefits, even in cooperatively breeding species where strong within-group incest avoidance is considered to be the norm.


Assuntos
Mamíferos/fisiologia , Comportamento Sexual Animal , Animais , Feminino , Masculino , Dados de Sequência Molecular
12.
Mol Ecol ; 23(16): 3999-4017, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25041117

RESUMO

Although the grey seal Halichoerus grypus is one of the most familiar and intensively studied of all pinniped species, its global population structure remains to be elucidated. Little is also known about how the species as a whole may have historically responded to climate-driven changes in habitat availability and anthropogenic exploitation. We therefore analysed samples from over 1500 individuals collected from 22 colonies spanning the Western and Eastern Atlantic and the Baltic Sea regions, represented by 350 bp of the mitochondrial hypervariable region and up to nine microsatellites. Strong population structure was observed at both types of marker, and highly asymmetrical patterns of gene flow were also inferred, with the Orkney Islands being identified as a source of emigrants to other areas in the Eastern Atlantic. The Baltic and Eastern Atlantic regions were estimated to have diverged a little over 10 000 years ago, consistent with the last proposed isolation of the Baltic Sea. Approximate Bayesian computation also identified genetic signals consistent with postglacial population expansion across much of the species range, suggesting that grey seals are highly responsive to changes in habitat availability.


Assuntos
Fluxo Gênico , Genética Populacional , Focas Verdadeiras/genética , Animais , Oceano Atlântico , Teorema de Bayes , DNA Mitocondrial/genética , Ecossistema , Repetições de Microssatélites , Dados de Sequência Molecular , Filogenia , Análise de Sequência de DNA
13.
J Evol Biol ; 26(10): 2233-43, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23980596

RESUMO

Correlations between heterozygosity and fitness are frequently found but rarely well understood. Fitness can be affected by single loci of large effect which correlate with neutral markers via linkage disequilibrium, or as a result of variation in genome-wide heterozygosity following inbreeding. We explored these alternatives in the common buzzard, a raptor species in which three colour morphs differ in their lifetime reproductive success. Using 18 polymorphic microsatellite loci, we evaluated potential genetic differences among the morphs which may lead to subpopulation structuring and tested for correlations between three fitness-related traits and heterozygosity, both genome wide and at each locus separately. Despite their assortative mating pattern, the buzzard morphs were found to be genetically undifferentiated. Multilocus heterozygosity was only found to be correlated with a single fitness-related trait, infection with the blood parasite, Leucocytozoon buteonis, and this was via interactions with vole abundance and age. One locus also showed a significant relationship with blood parasite infection and ectoparasite infestation. The vicinity of this locus contains two genes, one of which is potentially implicated in the immune system of birds. We conclude that genome-wide heterozygosity is unlikely to be a major determinant of parasite burden and body condition in the polymorphic common buzzard.


Assuntos
Falconiformes/genética , Heterozigoto , Animais , Cor , Falconiformes/parasitologia , Plumas/anatomia & histologia , Genoma , Endogamia , Repetições de Microssatélites , Carga Parasitária , Polimorfismo Genético , Comportamento Sexual Animal
14.
Sci Rep ; 2: 659, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22997548

RESUMO

The Major Histocompatability Complex (MHC) is one of the best known and best characterised components of the immune system, yet its functions remain somewhat enigmatic, including both anti-pathogen activity and kin recognition. To explore the importance of the MHC relative to literally hundreds of other components of the immune system, we compared MHC genotype frequencies between pups and adults in the grey seal (Halichoerus grypus), one of many marine mammals that exhibit low allelic diversity. We find that one allele is strongly associated with pup survival, pups being more likely to be found dead if they lack it, while total allele number is a remarkably strong predictor of survivorship to adulthood. We estimate that approximately 70% of mortality can be attributed to the MHC. Our study therefore shows that low MHC allele diversity belies its critical role in determining whether a weaned pup negotiates disease to become a breeding adult.


Assuntos
Complexo Principal de Histocompatibilidade , Focas Verdadeiras/genética , Análise de Variância , Animais , Feminino , Frequência do Gene , Variação Genética , Heterozigoto , Masculino , Mortalidade , Focas Verdadeiras/imunologia , Análise de Sobrevida , Reino Unido
15.
Mol Ecol Resour ; 12(5): 861-72, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22727236

RESUMO

Although single nucleotide polymorphisms (SNPs) are increasingly being recognized as powerful molecular markers, their application to non-model organisms can bring significant challenges. Among these are imperfect conversion rates of assays designed from in silico resources and the enhanced potential for genotyping error relative to pre-validated, highly optimized human SNPs. To explore these issues, we used Illumina's GoldenGate assay to genotype 480 Antarctic fur seal (Arctocephalus gazella) individuals at 144 putative SNPs derived from a 454 transcriptome assembly. One hundred and thirty-five polymorphic SNPs (93.8%) were automatically validated by the program GenomeStudio, and the initial genotyping error rate, estimated from nine replicate samples, was 0.004 per reaction. However, an almost tenfold further reduction in the error rate was achieved by excluding 31 loci (21.5%) that exhibited unclear clustering patterns, manually editing clusters to allow rescoring of ambiguous or incorrect genotypes, and excluding 18 samples (3.8%) with unreliable genotypes. After stringent quality filtering, we also found a counter-intuitive negative relationship between in silico minor allele frequency and the conversion rate, suggesting that some of our assays may have been designed from paralogous loci. Nevertheless, we obtained over 45 000 individual SNP genotypes with a final error rate of 0.0005, indicating that the GoldenGate assay is eminently capable of generating large, high-quality data sets for non-model organisms. This has positive implications for future studies of the evolutionary, behavioural and conservation genetics of natural populations.


Assuntos
Otárias/classificação , Otárias/genética , Biologia Molecular/métodos , Polimorfismo de Nucleotídeo Único , Animais , Genótipo
16.
Ecol Evol ; 3(1): 18-37, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23403722

RESUMO

Patterns of genetic variation observed within species reflect evolutionary histories that include signatures of past demography. Understanding the demographic component of species' history is fundamental to informed management because changes in effective population size affect response to environmental change and evolvability, the strength of genetic drift, and maintenance of genetic variability. Species experiencing anthropogenic population reductions provide valuable case studies for understanding the genetic response to demographic change because historic changes in the census size are often well documented. A classic example is the bowhead whale, Balaena mysticetus, which experienced dramatic population depletion due to commercial whaling in the late 19th and early 20th centuries. Consequently, we analyzed a large multi-marker dataset of bowhead whales using a variety of analytical methods, including extended Bayesian skyline analysis and approximate Bayesian computation, to characterize genetic signatures of both ancient and contemporary demographic histories. No genetic signature of recent population depletion was recovered through any analysis incorporating realistic mutation assumptions, probably due to the combined influences of long generation time, short bottleneck duration, and the magnitude of population depletion. In contrast, a robust signal of population expansion was detected around 70,000 years ago, followed by a population decline around 15,000 years ago. The timing of these events coincides to a historic glacial period and the onset of warming at the end of the last glacial maximum, respectively. By implication, climate driven long-term variation in Arctic Ocean productivity, rather than recent anthropogenic disturbance, appears to have been the primary driver of historic bowhead whale demography.

17.
Mol Ecol ; 20(19): 3989-4008, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21895820

RESUMO

Emerging Bayesian analytical approaches offer increasingly sophisticated means of reconstructing historical population dynamics from genetic data, but have been little applied to scenarios involving demographic bottlenecks. Consequently, we analysed a large mitochondrial and microsatellite dataset from the Antarctic fur seal Arctocephalus gazella, a species subjected to one of the most extreme examples of uncontrolled exploitation in history when it was reduced to the brink of extinction by the sealing industry during the late eighteenth and nineteenth centuries. Classical bottleneck tests, which exploit the fact that rare alleles are rapidly lost during demographic reduction, yielded ambiguous results. In contrast, a strong signal of recent demographic decline was detected using both Bayesian skyline plots and Approximate Bayesian Computation, the latter also allowing derivation of posterior parameter estimates that were remarkably consistent with historical observations. This was achieved using only contemporary samples, further emphasizing the potential of Bayesian approaches to address important problems in conservation and evolutionary biology.


Assuntos
Otárias/genética , Animais , Teorema de Bayes , Conservação dos Recursos Naturais , DNA Mitocondrial/química , Otárias/fisiologia , Genótipo , Repetições de Microssatélites , Densidade Demográfica , Dinâmica Populacional
18.
Mol Ecol ; 20(4): 740-52, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21199032

RESUMO

Pathogen-driven balancing selection maintains high genetic diversity in many vertebrates, particularly in the major histocompatibility complex (MHC) immune system gene family, which is often associated with disease susceptibility. In large natural populations where subpopulations face different pathogen pressures, the MHC should show greater genetic differentiation within a species than neutral markers. We examined genetic diversity at the MHC-DQB locus and nine putatively neutral microsatellite markers in grey seals (Halichoerus grypus) from eight United Kingdom (UK) colonies, the Faeroe Islands and Sable Island, Canada. Five DQB alleles were identified in grey seals, which varied in prevalence across the grey seal range. Among the seal colonies, significant differences in DQB allele and haplotype frequencies and in average DQB heterozygosity were observed. Additionally, the DQB gene exhibited greater differentiation among colonies compared with neutral markers, yet a weaker pattern of isolation by distance (IBD). After correcting for the underlying IBD pattern, subpopulations breeding in similar habitats were more similar to one another in DQB allele frequencies than populations breeding in different habitats, but the same did not hold true for microsatellites, suggesting that habitat-specific pathogen pressure influences MHC evolution. Overall, the data are consistent with selection at MHC-DQB loci in grey seals with both varying selective pressures and geographic population structure appearing to influence the DQB genetic composition of breeding colonies.


Assuntos
Variação Genética , Genética Populacional , Complexo Principal de Histocompatibilidade/genética , Focas Verdadeiras/genética , Animais , Sequência de Bases , Canadá , Dinamarca , Ecossistema , Frequência do Gene , Genes MHC da Classe II , Geografia , Repetições de Microssatélites , Dados de Sequência Molecular , Alinhamento de Sequência , Análise de Sequência de DNA , Reino Unido
19.
Proc Biol Sci ; 278(1709): 1183-8, 2011 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-20926441

RESUMO

Technological developments allow increasing numbers of markers to be deployed in case-control studies searching for genetic factors that influence disease susceptibility. However, with vast numbers of markers, true 'hits' may become lost in a sea of false positives. This problem may be particularly acute for infectious diseases, where the control group may contain unexposed individuals with susceptible genotypes. To explore this effect, we used a series of stochastic simulations to model a scenario based loosely on bovine tuberculosis. We find that a candidate gene approach tends to have greater statistical power than studies that use large numbers of single nucleotide polymorphisms (SNPs) in genome-wide association tests, almost regardless of the number of SNPs deployed. Both approaches struggle to detect genetic effects when these are either weak or if an appreciable proportion of individuals are unexposed to the disease when modest sample sizes (250 each of cases and controls) are used, but these issues are largely mitigated if sample sizes can be increased to 2000 or more of each class. We conclude that the power of any genotype-phenotype association test will be improved if the sampling strategy takes account of exposure heterogeneity, though this is not necessarily easy to do.


Assuntos
Simulação por Computador , Predisposição Genética para Doença , Modelos Genéticos , Tuberculose Bovina/genética , Animais , Bovinos , Marcadores Genéticos , Genótipo , Repetições de Microssatélites , Polimorfismo de Nucleotídeo Único , Processos Estocásticos
20.
Proc Biol Sci ; 277(1678): 131-7, 2010 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-19812086

RESUMO

There is a strong consensus that modern humans originated in Africa and moved out to colonize the world approximately 50 000 years ago. During the process of expansion, variability was lost, creating a linear gradient of decreasing diversity with increasing distance from Africa. However, the exact way in which this loss occurred remains somewhat unclear: did it involve one, a few or a continuous series of population bottlenecks? We addressed this by analysing a large published dataset of 783 microsatellite loci genotyped in 53 worldwide populations, using the program 'Bottleneck'. Immediately following a sharp population decline, rare alleles are lost faster than heterozygosity, creating a transient excess of heterozygosity relative to allele number, a feature that is used by Bottleneck to infer historical events. We find evidence of two primary events, one 'out of Africa' and one placed around the Bering Strait, where an ancient land bridge allowed passage into the Americas. These findings agree well with the regions of the world where the largest founder events might have been expected, but contrast with the apparently smooth gradient of variability that is revealed when current heterozygosity is plotted against distance from Africa.


Assuntos
Variação Genética/genética , Repetições de Microssatélites/genética , Modelos Genéticos , Modelos Estatísticos , Alelos , Genética Populacional , Humanos
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