scholarly journals The Sensitiveness of Expected Heterozygosity and Allelic Richness Estimates for Analyzing Population Genetic Diversity

2021 ◽  
Author(s):  
María Eugenia Barrandeguy ◽  
María Victoria García
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Genetic Variability ◽  
Population Size ◽  
Genetic Drift ◽  
Population Genetic ◽  
Allelic Richness ◽  
Theoretical Background ◽  
Computational Simulations ◽  
Expected Heterozygosity

Genetic diversity comprises the total of genetic variability contained in a population and it represents the fundamental component of changes since it determines the microevolutionary potential of populations. There are several measures for quantifying the genetic diversity, most notably measures based on heterozygosity and measures based on allelic richness, i.e. the expected number of alleles in populations of same size. These measures differ in their theoretical background and, in consequence, they differ in their ecological and evolutionary interpretations. Therefore, in the present chapter these measures of genetic diversity were jointly analyzed, highlighting the changes expected as consequence of gene flow and genetic drift. To develop this analysis, computational simulations of extreme scenarios combining changes in the levels of gene flow and population size were performed.

scholarly journals Evaluation of the Romosinuano cattle population structure in Mexico using pedigree analysis

2020 ◽  
Vol 33 (1) ◽  
pp. 44-59
Author(s):  
Rafael Núñez-Domínguez ◽  
Ricardo E Martínez-Rocha ◽  
Jorge A Hidalgo-Moreno ◽  
Rodolfo Ramírez-Valverde ◽  
José G García-Muñiz
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Gene Flow ◽  
Population Size ◽  
Effective Population Size ◽  
Genetic Drift ◽  
Pedigree Analysis ◽  
Effective Population ◽  
Genetic Management ◽  
Generation Interval

Background: Romosinuano cattle breed in Mexico has endured isolation and it is necessary to characterize it in order to facilitate sustainable genetic management. Objective: To assess the evolution of the structure and genetic diversity of the Romosinuano breed in Mexico, through pedigree analysis. Methods: Pedigree data was obtained from Asociación Mexicana de Criadores de Ganado Romosinuano y Lechero Tropical (AMCROLET). The ENDOG program (4.8 version) was used to analyze two datasets, one that includes upgrading from F1 animals (UP) and the other with only straight-bred cattle (SP). For both datasets, three reference populations were defined: 1998-2003 (RP1), 2004-2009 (RP2), and 2010-2017 (RP3). The pedigree included 3,432 animals in UP and 1,518 in SP. Demographic parameters were: Generation interval (GI), equivalent number of generations (EG), pedigree completeness index (PCI), and gene flow among herds. Genetic parameters were: Inbreeding (F) and average relatedness (AR) coefficients, effective population size (Nec), effective number of founders and ancestors, and number of founder genome equivalents. Results: The GI varied from 6.10 to 6.54 for UP, and from 6.47 to 7.16 yr for SP. The EG of the UP and SP improved >63% from RP1 to RP3. The PCI increased over time. No nucleus or isolated herds were found. For RP3, F and AR reached 2.08 and 5.12% in the UP, and 2.55 and 5.94% in the SP. For RP3, Nec was 57 in the UP and 45 in the SP. Genetic diversity losses were attributed mainly (>66%) to genetic drift, except for RP3 in the SP (44%). Conclusions: A reduction of the genetic diversity has been occurring after the Romosinuano breed association was established in Mexico, and this is mainly due to random loss of genes.Keywords: effective population size; gene flow; genetic diversity; genetic drift; generation interval; inbreeding; pedigree; population structure; probability of gene origin; Romosinuano cattle. Resumen Antecedentes: La raza bovina Romosinuano ha estado prácticamente aislada en México y requiere ser caracterizada para un manejo genético sostenible. Objetivo: Evaluar la evolución de la estructura y diversidad genética de la raza Romosinuano en México, mediante el análisis del pedigrí. Métodos: Los datos genealógicos provinieron de la Asociación Mexicana de Criadores de Ganado Romosinuano y Lechero Tropical (AMCROLET). Los análisis se realizaron con el programa ENDOG (versión 4.8) para dos bases de datos, una que incluyó animales en cruzamiento absorbente (UP) a partir de F1 y la otra con sólo animales puros (SP). Para ambas bases de datos se definieron tres poblaciones de referencia: 1998-2003 (RP1), 2004- 2009 (RP2), y 2010-2017 (RP3). El pedigrí incluyó 3.432 animales en la UP y 1.518 en la SP. Los parámetros demográficos fueron: intervalo generacional (GI), número de generaciones equivalentes (EG), índice de completitud del pedigrí (PCI), y flujo de genes entre hatos. Los parámetros genéticos fueron: coeficientes de consanguinidad (F) y de relación genética aditiva (AR), tamaño efectivo de la población (Nec), número efectivo de fundadores y ancestros, y número equivalente de genomas fundadores. Resultados: El GI varió de 6,10 a 6,54 para la UP, y de 6,47 a 7,16 años para la SP. El EG de la UP y la SP mejoró >63%, de RP1 a RP3. El PCI aumentó a través de los años, pero más para la SP que para la UP. No se encontraron hatos núcleo o aislados. Para RP3, F y AR alcanzaron 2,08 y 5,12% en la UP, y 2,55 y 5,94% en la SP. Para RP3, Nec fue 57 en la UP y 45 en la SP. Más de 66% de las pérdidas en diversidad genética se debieron a deriva genética, excepto para RP3 en la UP (44%). Conclusiones: una reducción de la diversidad genética ha estado ocurriendo después de que se formó la asociación de criadores de ganado Romosinuano en México, y es debida principalmente a pérdidas aleatorias de genes.Palabras clave: consanguinidad; deriva genética; diversidad genética; estructura poblacional; flujo de genes; ganado Romosinuano; intervalo generacional; pedigrí; probabilidad de origen del gen; tamaño efectivo de población. Resumo Antecedentes: A raça bovina Romosinuano tem estado praticamente isolada no México e precisa ser caracterizada para um manejo genético sustentável. Objetivo: Avaliar a evolução da estrutura e diversidade genética da raça Romosinuano no México, através da análise de pedigree. Métodos: Os dados genealógicos vieram da Asociación Mexicana de Criadores de Ganado Romosinuano y Lechero Tropical (AMCROLET). As análises foram feitas com o programa ENDOG (versão 4.8) para duas bases de dados, uma que incluiu animais em cruzamento absorvente (UP) a partir da F1 e a outra base de dados somente com animais puros (SP). Para ambas bases de dados foram definidas três populações de referência: 1998-2003 (RP1), 2004-2009 (RP2) e 2010-2017 (RP3). O pedigree incluiu 3.432 animais na UP e 1.518 na SP. Os parâmetros demográficos foram: intervalo entre gerações (GI), número de gerações equivalentes (EG), índice de completude do pedigree (PCI), e fluxo de genes entre rebanhos. Os parâmetros genéticos foram: coeficiente de consanguinidade (F) e da relação genética aditiva (AR), tamanho efetivo da população (Nec), número efetivo de fundadores e ancestrais, e número equivalente de genomas fundadores. Resultados: O GI variou de 6,10 a 6,54 para a UP, e de 6,47 a 7,16 anos para a SP. EG da UP e a SP melhorou >63%, de RP1 a RP3. O PCI aumentou ao longo dos anos, mas mais para a SP do que para o UP. Não se encontraram rebanhos núcleo ou isolados. Para RP3, F e AR alcançaram 2,08 e 5,12% na UP, e 2,55 e 5,94% na SP. Para RP3, Nec foi 57 na UP e 45 na SP. Mais de 66% das perdas em diversidade genética foram ocasionadas pela deriva genética, exceto para RP3 no UP (44%). Conclusões: Depois que a associação da raça Romosinuano foi estabelecida no México, tem ocorrido uma redução da diversidade genética, principalmente devido a perdas aleatórias de genes.Palavras-chave: consanguinidade; deriva genética; diversidade genética, estrutura populacional; fluxo de genes; intervalo entre gerações; pedigree; probabilidade de origem do gene; Romosinuano; tamanho efetivo da população.

scholarly journals Differentiation with drift: a spatio-temporal genetic analysis of Galápagos mockingbird populations ( Mimus spp.)

2010 ◽  
Vol 365 (1543) ◽  
pp. 1127-1138 ◽  
Author(s):  
Paquita E. A. Hoeck ◽  
Jennifer L. Bollmer ◽  
Patricia G. Parker ◽  
Lukas F. Keller
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Population Size ◽  
Genetic Drift ◽  
Bird Species ◽  
Effective Population ◽  
Island Size ◽  
Island Populations ◽  
Population Sizes ◽  
Spatio Temporal

Small and isolated island populations provide ideal systems to study the effects of limited population size, genetic drift and gene flow on genetic diversity. We assessed genetic diversity within and differentiation among 19 mockingbird populations on 15 Galápagos islands, covering all four endemic species, using 16 microsatellite loci. We tested for signs of drift and gene flow, and used historic specimens to assess genetic change over the last century and to estimate effective population sizes. Within-population genetic diversity and effective population sizes varied substantially among island populations and correlated strongly with island size, suggesting that island size serves as a good predictor for effective population size. Genetic differentiation among populations was pronounced and increased with geographical distance. A century of genetic drift did not change genetic diversity on an archipelago-wide scale, but genetic drift led to loss of genetic diversity in small populations, especially in one of the two remaining populations of the endangered Floreana mockingbird. Unlike in other Galápagos bird species such as the Darwin's finches, gene flow among mockingbird populations was low. The clear pattern of genetically distinct populations reflects the effects of genetic drift and suggests that Galápagos mockingbirds are evolving in relative isolation.

scholarly journals Population differentiation and gene flow in Rrodium cicutarium: A potential medicinal plant

Genetika ◽  
2020 ◽  
Vol 52 (3) ◽  
pp. 1127-1144 ◽  
Author(s):  
Yaocheng Jia ◽  
Majid Khayatnezhad ◽  
Shahram Mehri
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Genetic Variability ◽  
Population Genetic ◽  
Morphological Variability ◽  
Morphological Characteristics ◽  
Assignment Test ◽  
Population Genetic Differentiation ◽  
Irap Markers ◽  
Geographical Populations

Erodium (Geranaiceae) species are distributed in different habitats of Iran. Some species are of medicinal importance while some are well known weeds. In arid and semi-arid regions, E. cicutarium has had some importance as a forage plant and is an important grazing plant and source of protein supplements to straw for ruminants in semi deserts and wastelands of the Middle East. There is no information on its population genetic structure, genetic diversity, and morphological variability in Iran. Due to the medicinal importance of this species, a genetic variability and populations? structure study is performed studying 15 geographical populations of E. cicutarium Therefore, we used six inter-retrotransposon amplified polymorphism (IRAP) markers and 15 combined IRAP markers to reveal within and among population genetic diversity in this plant. AMOVA test produced significant genetic difference (PhiPT = 0.39, P = 0.010) among the studied populations and also revealed that, 55% of total genetic variability was due to within population diversity while, 45% was due to among population genetic differentiation. Mantel test showed positive significant correlation between genetic distance and geographical distance of the studied populations. Networking, STRUCTURE analyses and population assignment test revealed some degree of gene flow among these populations. PCoA plot of populations based on morphological characters was in agreement with MDS plot of molecular data. These results indicated that geographical populations of E. cicutarium are well differentiated both in genetic content as well as morphological characteristics. Consensus tree based on morphological and genetic data separated some of these populations from the others suggesting the existence of ecotypes within this species.

scholarly journals Genetic diversity and relationship among indigenous Turkish Karayaka sheep subpopulations

2020 ◽  
Vol 63 (2) ◽  
pp. 269-275
Author(s):  
Koray Kirikci ◽  
M. Akif Cam ◽  
Levent Mercan
Keyword(s):  
Genetic Diversity ◽  
Population Genetic ◽  
Allelic Richness ◽  
Genetic Difference ◽  
Genetic Relationships ◽  
Inbreeding Coefficient ◽  
The Black Sea ◽  
Breeding Strategies ◽  
Black Sea Region ◽  
Expected Heterozygosity

Abstract. The Karayaka is the most populous sheep breed in the Black Sea region of Turkey. In the present study, we investigated the intra- and inter-population genetic relationships among indigenous Karayaka sheep subpopulations. Nine microsatellites were genotyped for 64 individuals from Samsun, Ordu, Giresun and Tokat provinces. The average number of alleles (Na), allelic richness (Ar), observed heterozygosity (Ho), expected heterozygosity (He), polymorphism information content (PIC) and inbreeding coefficient (FIS) for all subpopulations were estimated as Na=16.44, Ar=9.887, Ho=0.303, He=0.886, PIC=0.866 and FIS=0.630, respectively. The observed and expected heterozygosity ranged from 0.171 (Giresun) to 0.376 (Ordu) and 0.757 (Samsun) to 0.845 (Ordu), respectively. It was determined that a 10.5 % of total genetic variation (FIT=66.9 %) in Karayaka sheep corresponded to genetic differences among subpopulations (FST), whereas 63.0 % was explained by genetic difference among individuals (FIS). This study gives the first evidence about genetic relationships of Karayaka subpopulations. The results show that Karayaka sheep subpopulations are genetically different from each other. These findings revealed that the Karayaka breed has discrete subpopulations and should be taken into consideration when preparing conservation programs and future breeding strategies.

scholarly journals Genetic Diversity and Population Structure of Bermudagrass [Cynodon dactylon (L.) Pers.] along Latitudinal Gradients and the Relationship with Polyploidy Level

Diversity ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 135 ◽  
Author(s):  
Jingxue Zhang ◽  
Miaoli Wang ◽  
Zhipeng Guo ◽  
Yongzhuo Guan ◽  
Jianyu Liu ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Gene Flow ◽  
Population Genetic ◽  
Cynodon Dactylon ◽  
Latitudinal Gradients ◽  
Wind Pollination ◽  
Ploidy Levels ◽  
Sexual And Asexual Reproduction ◽  
Genetic Pattern

Understanding the population genetic pattern and process of gene flow requires a detailed knowledge of how landscape characteristics structure populations. Although Cynodon dactylon (L.) Pers. (common bermudagrass) is widely distributed in the world, information on its genetic pattern and population structure along latitudinal gradients is limited. We tried to estimate the genetic diversity and genetic structure of C. dactylon along a latitudinal gradient across China. Genetic diversity among different ploidy levels was also compared in the study. The material used consisted of 296 C. dactylon individuals sampled from 16 geographic sites from 22°35′ N to 36°18′ N. Genetic diversity was estimated using 153 expressed sequence tag-derived simple sequence repeat (EST-SSR) loci. Higher within-population genetic diversity appeared at low-latitude, as well as having positive correlation with temperature and precipitation. The genetic diversity increased with the ploidy level of C. dactylon, suggesting polyploidy creates higher genetic diversity. No isolation by distance and notable admixture structure existed among populations along latitudes. Both seed dispersal (or vegetative organs) and extrinsic pollen played important roles for gene flow in shaping the spatial admixture population structure of C. dactylon along latitudes. In addition, populations were separated into three clusters according to ploidy levels. C. dactylon has many such biological characters of perennial growth, wind-pollination, polyploidy, low genetic differentiation among populations, sexual and asexual reproduction leading to higher genetic diversity, which gives it strong adaptability with its genetic patterns being very complex across all the sampled latitudes. The findings of this study are related to landscape population evolution, polyploidy speciation, preservation, and use of bermudagrass breeding.

Use of expressed sequence tag microsatellite markers for population genetic research of Helicoverpa armigera (Lepidoptera: Noctuidae) from India

2015 ◽  
Vol 148 (2) ◽  
pp. 187-199
Author(s):  
Thiruvengadam Venkatesan ◽  
Vaddi Sridhar ◽  
Yan R. Tomason ◽  
Sushil Kumar Jalali ◽  
Gajanan T. Behere ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Microsatellite Markers ◽  
Population Genetic ◽  
Expressed Sequence Tag ◽  
Genetic Research ◽  
Western India ◽  
Diversity Analysis ◽  
Lepidoptera Noctuidae ◽  
Expressed Sequence

AbstractCotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a serious pest of several crops throughout the world, representing millions of United States of America dollars worth of damage. This pest can adapt to various cropping systems in a wide geographical range and has high migratory potential. It features high fecundity and can develop resistance to almost all insecticides used for its management. Several investigations to develop microsatellite markers for H. armigera have not been successful because of the paucity of microsatellites in the lepidopteran genome. As well, collections of H. armigera from cotton fields of southern and western India were not yet studied for molecular genetic diversity. The current study aimed to screen publicly available expressed sequence tag resources for simple sequence repeats and assess their potential as DNA markers for assessment of gene flow between collections of southern and western India. We identified 30 polymorphic microsatellites for potential use in diversity analysis of H. armigera collections. Genetic diversity analysis revealed that the collections were widely diverse with population differentiation index (Fst) of 0.17. Furthermore, gene flow analysis revealed a mean frequency of private alleles of 11% within the collections. The microsatellite resources we developed could be widely used for molecular diversity or population genetic research involving this important pest of cotton and food crops.

Genetic variation in the greater bilby (Macrotis lagotis)

1994 ◽  
Vol 1 (1) ◽  
pp. 46 ◽  
Author(s):  
Richard Southgate ◽  
Mark Adams
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Genetic Variability ◽  
Population Genetic ◽  
Taxonomic Status ◽  
Biological Species ◽  
Significant Loss ◽  
Allozyme Electrophoresis ◽  
Allozyme Data ◽  
Data Support

The taxonomic status of and genetic diversity amongst extant populations of the greater bilby, Macrotis lagotis, were assessed using allozyme electrophoresis. A total of 47 bilbies sampled from three geographic areas and two captive colonies were screened for 42 loci, six of which were polymorphic. The results are consistent with the view that all extant populations represent a single biological species. All populations were genetically very similar (Nei D's 0.000 to 0.004) and overall levels of within-population genetic variability were low (Ho 0.004 � 0.004 to 0.0026 � 0.017). The allozyme data support the hypothesis that there has been no significant loss of variability in the captive colonies when compared to the species as a whole.

Analysis of genetic diversity in four Canadian swine breeds using pedigree data

2010 ◽  
Vol 90 (3) ◽  
pp. 331-340 ◽  
Author(s):  
M G Melka ◽  
F. Schenkel
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Effective Population Size ◽  
Genetic Drift ◽  
Relative Proportion ◽  
Random Genetic Drift ◽  
Pedigree Data ◽  
Effective Population ◽  
Animal Genetic Resources ◽  
Loss Of Genetic Diversity

Conservation of animal genetic resources entails judicious assessment of genetic diversity as a first step. The objective of this study was to analyze the trend of within-breed genetic diversity and identify major causes of loss of genetic diversity in four swine breeds based on pedigree data. Pedigree files from Duroc (DC), Hampshire (HP), Lacombe (LC) and Landrace (LR) containing 480 191, 114 871, 51 397 and 1 080 144 records, respectively, were analyzed. Pedigree completeness, quality and depth were determined. Several parameters derived from the in-depth pedigree analyses were used to measure trends and current levels of genetic diversity. Pedigree completeness indexes of the four breeds were 90.4, 52.7, 89.6 and 96.1%, respectively. The estimated percentage of genetic diversity lost within each breed over the last three decades was approximately 3, 22, 12 and 2%, respectively. The relative proportion of genetic diversity lost due to random genetic drift in DC, HP, LC and LR was 74.5, 63.6, 72.9 and 60.0%, respectively. The estimated current effective population size for DC, HP, LC and LR was 72, 14, 36 and 125, respectively. Therefore, HP and LC have been found to have lost considerable genetic diversity, demanding priority for conservation. Key words: Genetic drift, effective population size

Conservation genetics and ecology of the endangered rainforest shrub, Triunia robusta, from the Sunshine Coast, Australia

2002 ◽  
Vol 50 (1) ◽  
pp. 93 ◽  
Author(s):  
Alison Shapcott
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Gene Flow ◽  
Conservation Genetics ◽  
Population Size ◽  
Genetic Similarity ◽  
Small Region ◽  
Geographic Proximity ◽  
Close Proximity ◽  
The Mean

Triunia robusta, which until recently was thought to be extinct, is now classified nationally as endangered. It is an understorey species restricted to the subcoastal rainforests in a small region of the Sunshine Coast, Queensland. The project involved sampling the genetic variation and measuring the population size and size distribution of T. robusta and its geographically closest congener T. youngiana, which occurs further south and has a wider geographic distribution. A total of 877 T. robusta plants were recorded across the 11 populations, approximately half (56.8%) of these were juveniles less than 1 m tall, whereas in T. youngiana only about 36.4% of a population was composed of juveniles. Genetic diversity was similar but significantly higher for T. robusta than T. youngiana if the very small T. robusta populations (2 or 3 plants) were excluded from analysis (P < 0.05). The mean percentage of polymorphic loci among populations was high for both species. Triunia robusta is not, on average, more inbred than the more common T. youngiana. There was more differentiation between the T. robusta populations, which were in close proximity, than between the more geographically separated T. youngiana populations. Thus, there is evidence of more gene flow between populations of T. youngiana than between those of T. robusta. However, there was no geographic relationship between genetic similarity and geographic proximity in T. robusta

scholarly journals Genetic Resilience of a Once Endangered Species, Tibetan Antelope (Pantholops hodgsonii)

2019 ◽  
Author(s):  
Yue Shi ◽  
Jiarui Chen ◽  
Jianping Su ◽  
Tongzuo Zhang ◽  
Samuel K. Wasser
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Population Size ◽  
Effective Population Size ◽  
Genetic Bottleneck ◽  
Migration Routes ◽  
Effective Population ◽  
Human Disturbances ◽  
Population Reduction ◽  
Tibetan Antelope

AbstractPopulation reduction is generally assumed to reduce the population’s genetic diversity and hence its ability to adapt to environmental change. However, if life history traits that promote gene flow buffer populations from such impacts, conservation efforts should aim to maintain those traits in vulnerable species. Tibetan antelope (Pantholops hodgsonii) has experienced population reduction by 95% due to poaching during the 20th century. We hypothesize that opportunities for gene flow provided by their sex-specific migration buffered their genetic diversity from the poaching impacts. We measured the mtDNA (control region, CR) and nuDNA (microsatellites or STRs) diversity, population differentiation, along with the change in effective population size (pre-poaching era vs. post-poaching era) and tested for a genetic bottleneck. Our results showed that Tibetan antelope maintained considerable genetic diversity in both mtDNA CR and STR markers (Hd = 0.9970 and Hobs = 0.8446, respectively), despite a marked reduction in post-poaching effective population size 368.9 (95% CI of 249.3 - 660.6) compared to the pre-poaching average (4.93×103 - 4.17×104). Post-poached populations also had low population structure and showed no evidence of a genetic bottleneck. Pairwise Fst values using CR haplotype frequencies were higher than those using STR allele frequencies, suggesting different degrees of gene flow mediated by females and males. This study suggests that the Tibetan antelope’s sex-specific migration buffered their loss of genetic diversity in the face of severe demographic decline. These findings highlight the importance of recognizing the traits likely to maintain genetic diversity and promoting conservation efforts that allow them to be exercised. For Tibetan antelope, this requires assuring that their migration routes remain unobstructed by growing human disturbances while continuing to enforce anti-poaching law enforcement efforts.

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