scholarly journals Evaluating the use of ABBA-BABA statistics to locate introgressed loci

2013 ◽  
Author(s):  
Simon H. Martin ◽  
John W. Davey ◽  
Chris D. Jiggins

Several methods have been proposed to test for introgression across genomes. One method tests for a genome-wide excess of shared derived alleles between taxa using Patterson?s D statistic, but does not establish which loci show such an excess or whether the excess is due to introgression or ancestral population structure. Several recent studies have extended the use of D by applying the statistic to small genomic regions, rather than genome-wide. Here, we use simulations and whole genome data from Heliconius butterflies to investigate the behavior of D in small genomic regions. We find that D is unreliable in this situation as it gives inflated values when effective population size is low, causing D outliers to cluster in genomic regions of reduced diversity. As an alternative, we propose a related statistic f̂d, a modified version of a statistic originally developed to estimate the genome-wide fraction of admixture. f̂d is not subject to the same biases as D, and is better at identifying introgressed loci. Finally, we show that both D and f̂d outliers tend to cluster in regions of low absolute divergence (dXY), which can confound a recently proposed test for differentiating introgression from shared ancestral variation at individual loci.

Genes ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 577
Author(s):  
Huiwen Zhan ◽  
Saixian Zhang ◽  
Kaili Zhang ◽  
Xia Peng ◽  
Shengsong Xie ◽  
...  

Investigating the patterns of homozygosity, linkage disequilibrium, effective population size and inbreeding coefficients in livestock contributes to our understanding of the genetic diversity and evolutionary history. Here we used Illumina PorcineSNP50 Bead Chip to identify the runs of homozygosity (ROH) and estimate the linkage disequilibrium (LD) across the whole genome, and then predict the effective population size. In addition, we calculated the inbreeding coefficients based on ROH in 305 Piétrain pigs and compared its effect with the other two types of inbreeding coefficients obtained by different calculation methods. A total of 23,434 ROHs were detected, and the average length of ROH per individual was about 507.27 Mb. There was no regularity on how those runs of homozygosity distributed in genome. The comparisons of different categories suggested that the formation of long ROH was probably related with recent inbreeding events. Although the density of genes located in ROH core regions is lower than that in the other genomic regions, most of them are related with Piétrain commercial traits like meat qualities. Overall, the results provide insight into the way in which ROH is produced and the identified ROH core regions can be used to map the genes associated with commercial traits in domestic animals.


PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0246497
Author(s):  
Vandana Manomohan ◽  
Ramasamy Saravanan ◽  
Rudolf Pichler ◽  
Nagarajan Murali ◽  
Karuppusamy Sivakumar ◽  
...  

The present study is the first comprehensive report on diversity, population structure, genetic admixture and mitochondrial DNA variation in South Indian draught type zebu cattle. The diversity of South Indian cattle was moderately high. A significantly strong negative correlation coefficient of -0.674 (P<0.05) was observed between the effective population size of different breeds and their estimated FIS. The genetic structure analysis revealed the distinctness of Kangayam, Vechur and Punganur cattle from the rest of the zebu breeds. The results showed the influence of Hallikar breed in the development of most Mysore type cattle breeds of South India with the exception of Kangayam. Bayesian clustering analysis was performed to assess the taurine admixture in South Indian zebu cattle using purebred Jersey and Holstein-Friesian as reference genotypes. Relatively high levels of taurine admixture (>6.25%) was observed in Punganur, Vechur, Umblachery and Pulikulam cattle breeds. Two major maternal haplogroups, I1 and I2, typical of zebu cattle were observed, with the former being predominant than the later. The pairwise differences among the I2 haplotypes of South Indian cattle were relatively higher than West Indian (Indus valley site) zebu cattle. The results indicated the need for additional sampling and comprehensive analysis of mtDNA control region variations to unravel the probable location of origin and domestication of I2 zebu lineage. The present study also revealed major concerns on South Indian zebu cattle (i) risk of endangerment due to small effective population size and high rate of inbreeding (ii) lack of sufficient purebred zebu bulls for breeding and (iii) increasing level of taurine admixture in zebu cattle. Availability of purebred semen for artificial insemination, incorporation of genomic/molecular information to identify purebred animals and increased awareness among farmers will help to maintain breed purity, conserve and improve these important draught cattle germplasms of South India.


2011 ◽  
Vol 54 (1) ◽  
pp. 1-9
Author(s):  
L. Vostrý ◽  
Z. Čapková ◽  
J. Přibyl ◽  
B. Hofmanová ◽  
H. Vostrá Vydrová ◽  
...  

Abstract. In order to estimate effective population size, generation interval and the development of inbreeding coefficients (Fx) in three original breeds of cold-blooded horses kept in the Czech Republic: Silesian Noriker (SN), Noriker (N) and Czech-Moravian Belgian horse (CMB) all animals of the particular breeds born from 1990 to 2007 were analysed. The average values of generation interval between parents and their offspring were: 8.53 in SN, 8.88 in N and 8.56 in CMB. Average values of effective population size were estimated to be: 86.3 in SN, 162.3 in N and 104.4 in CMB. The average values of inbreeding coefficient were 3.13 % in SN stallions and 3.39 % in SN mares, in the N breed 1.76 % and 1.26 % and in the CMB breed 3.84 % and 3.26 % respectively. Overall averages of Fx were: 3.23 %, 1.51 % and 3.55 % for the breeds SN, N and CMB. The average value of inbreeding coefficient Fx increased by 1.22 % in SN, by 0.35 % in N and by 1.01 % in CMB, respectively. This may lead to a reduction in genetic variability. Reduction in genetic variability could be either controlled in cooperation with corresponding populations of cold-blooded breeds in other European countries or controlled by number of sires used in population


PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10348
Author(s):  
Austin S. Chipps ◽  
Amanda M. Hale ◽  
Sara P. Weaver ◽  
Dean A. Williams

There are increasing concerns regarding bat mortality at wind energy facilities, especially as installed capacity continues to grow. In North America, wind energy development has recently expanded into the Lower Rio Grande Valley in south Texas where bat species had not previously been exposed to wind turbines. Our study sought to characterize genetic diversity, population structure, and effective population size in Dasypterus ega and D. intermedius, two tree-roosting yellow bats native to this region and for which little is known about their population biology and seasonal movements. There was no evidence of population substructure in either species. Genetic diversity at mitochondrial and microsatellite loci was lower in these yellow bat taxa than in previously studied migratory tree bat species in North America, which may be due to the non-migratory nature of these species at our study site, the fact that our study site is located at a geographic range end for both taxa, and possibly weak ascertainment bias at microsatellite loci. Historical effective population size (NEF) was large for both species, while current estimates of Ne had upper 95% confidence limits that encompassed infinity. We found evidence of strong mitochondrial differentiation between the two putative subspecies of D. intermedius (D. i. floridanus and D. i. intermedius) which are sympatric in this region of Texas, yet little differentiation using microsatellite loci. We suggest this pattern is due to secondary contact and hybridization and possibly incomplete lineage sorting at microsatellite loci. We also found evidence of some hybridization between D. ega and D. intermedius in this region of Texas. We recommend that our data serve as a starting point for the long-term genetic monitoring of these species in order to better understand the impacts of wind-related mortality on these populations over time.


Animals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1089
Author(s):  
Andreia J. Amaral ◽  
Ana L. Pavão ◽  
Luis T. Gama

Ramo Grande is a local cattle breed raised in the archipelago of Azores, with a small and dispersed census, where inbreeding control is of utmost importance. A single nucleotide polymorphism (SNP) Beadchip array was used to assess inbreeding, by analysis of genomic regions harboring contiguous homozygous genotypes named runs of homozygosity (ROH), and to estimate past effective population size by analysis of linkage disequilibrium (LD). Genetic markers associated with production traits were also investigated, exploiting the unique genetic and adaptation features of this breed. A total of 639 ROH with length >4 Mb were identified, with mean length of 14.96 Mb. The mean genomic inbreeding was 0.09, and long segments of ROH were common, indicating recent inbred matings. The LD pattern indicates a large effective population size, suggesting the inflow of exotic germplasm in the past. The genome-wide association study identified novel markers significantly affecting longevity, age at first calving and direct genetic effects on calf weight. These results provide the first evidence of the association of longevity with genes related with DNA recognition and repair, and the association of age at first calving with aquaporin proteins, which are known to have a crucial role in reproduction.


Author(s):  
Endalkachew Girma ◽  
Kefyalew Alemayehu ◽  
Solomon Abegaze ◽  
Damitie Kebede

SummaryThe study was carried out in selected districts in the Northwestern Amhara, from October 2012 to May 2013. The objective of the study were to undertake on-farm and on-station phenotypic characterization of Fogera Cattle in comparison with two different local cattle population, to characterize the population structure and to identifying trait preferences, breeding management and to recommend breeding strategy for Fogera cattle. Both purposive and random samplings were employed. Data were gathered through semi-structured questionnaire, focus group discussions, field observations, census data, direct count and body measurements. About 126 smallholder farmers were interviewed. About 21 quantitative and 17 qualitative phenotypic data types were also generated from 332 cattle. The Effective population size (Ne) and rate of inbreeding (ΔF) were calculated from the counted population structure data. Both GLM procedures of SAS and descriptive statistics of SPSS software's were employed for data analyses. The results indicated that Fogera cattle were kept mostly for milk (97.62 percent). The main threats identified for the survival of Fogera cattle were scarcity of feed resources and interbreeding with other indigenous cattle, which are less demanding in terms of feed. Fogera cattle population has specific morphological appearance. Generally about 65.2 percent of male pure-Fogera cattle population are having large hump and large dewlap (93.5 percent) with cervico-thoracic (82.6 percent) hump position and long tail (97.8 percent), respectively. The coat pattern of male pure-Fogera cattle is dominated by the spotted coat pattern (82.6 percent) with 43.5 percent white black and 39.1 percent black white coat colour. Female Fogera cattle have medium (94.4 percent) hump size at cervico-thoracic positions (73.2 percent), large dewlap (62.7 percent) and long tail which is well below the hock (91.5 percent). The coat pattern of female pure-Fogera cattle is dominated by white spotted (80.3 percent) with 43.0 percent white black and 33.1 percent black white coat colour Most of the quantitative traits were highly significantly (P≤ 0.001) affected by breed type. Except horn length and horn space all of quantitative traits for both sexes of pure-Fogera cattle from on-station were significantly (P≤ 0.05) larger than those of the on-farm. The average linear body measurement taken on a total of 46 male pure-Fogera cattle populations were 42.68 ± 0.56 cm (mouth circumference), 16.35 ± 0.72 cm (horn length), 37.04 ± 1.16 cm (dewlap width) and 129.17 ± 1.33 cm (height at wither). The average linear body measurements for female pure-Fogera cattle were 38.23 ± 0.18 cm (mouth circumference), 13.81 ± 0.37 cm (horn length), 27.20 ± 0.42 cm (dewlap width) and 123.68 ± 0.52 cm (height at wither). The population structure were dominated by Pure-Fogera constituting 37.02 percent, Interbred with Fogera (33.71 percent) and non-Fogera (29.23 percent). The effective population size of pure-Fogera cattle was 4295, with 9016 total population. The average inbreeding level for the population was 0.012 percent. Inbreeding is at a low level and the effective population size is large. The calculated parameters indicate satisfactory genetic diversity in Fogera cattle. Milk yield, colour, power, body size and growth rate of Fogera were the most dominant traits perceived to be good by the respondents. The special qualification of this breed is to live at high amount of flooding areas with adapting other very challenging environment. Pure breeding of pure-Fogera, interbred with Fogera and non-Fogera type of breeds was used for breeding practice with natural mating. The Andassa Research Center established in 1964 as Fogera cattle population improving centre, but according to different source, population viability and population structure indicated that the population are not viable and highly admixture with other indigenous cattle breeds. According to this in order to improve the population status of Fogera cattle we recommended control with open-nucleus breeding strategy. So in order to minimize the risk status of this breed and conserve for the future generation any responsible agent should be given priority.


1985 ◽  
Vol 17 (1) ◽  
pp. 97-106 ◽  
Author(s):  
John H. Relethford

SummaryA method is presented for examining the relationship between effective population size and accumulated random inbreeding in human populations. For a set of populations, the inverse of inbreeding is regressed on effective population size using a linear regression model. This procedure allows testing of several hypotheses regarding the common and unique influences on population structure. Deviations from the expected curve suggest demographic or historical change. This method is applied to surname data from nine Irish isolates. The results show that the method is very useful in assessing differential influences on population structure.


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