scholarly journals Historical effective population size of North American hoary bat (Lasiurus cinereus) and challenges to estimating trends in contemporary effective breeding population size from archived samples

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11285
Author(s):  
Robert S. Cornman ◽  
Jennifer A. Fike ◽  
Sara J. Oyler-McCance ◽  
Paul M. Cryan
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
North American ◽  
Breeding Population ◽  
Data Filtering ◽  
Effective Population ◽  
Data Set ◽  
Lasiurus Cinereus ◽  
The Impact ◽  
Hoary Bats

Background Hoary bats (Lasiurus cinereus) are among the bat species most commonly killed by wind turbine strikes in the midwestern United States. The impact of this mortality on species census size is not understood, due in part to the difficulty of estimating population size for this highly migratory and elusive species. Genetic effective population size (Ne) could provide an index of changing census population size if other factors affecting Ne are stable. Methods We used the NeEstimator package to derive effective breeding population size (Nb) estimates for two temporally spaced cohorts: 93 hoary bats collected in 2009–2010 and an additional 93 collected in 2017–2018. We sequenced restriction-site associated polymorphisms and generated a de novo genome assembly to guide the removal of sex-linked and multi-copy loci, as well as identify physically linked markers. Results Analysis of the reference genome with psmc suggested at least a doubling of Ne in the last 100,000 years, likely exceeding Ne = 10,000 in the Holocene. Allele and genotype frequency analyses confirmed that the two cohorts were comparable, although some samples had unusually high or low observed heterozygosities. Additionally, the older cohort had lower mean coverage and greater variability in coverage, and batch effects of sampling locality were observed that were consistent with sample degradation. We therefore excluded samples with low coverage or outlier heterozygosity, as well as loci with sequence coverage far from the mode value, from the final data set. Prior to excluding these outliers, contemporary Nb estimates were significantly higher in the more recent cohort, but this finding was driven by high values for the 2018 sample year and low values for all other years. In the reduced data set, Nb did not differ significantly between cohorts. We found base substitutions to be strongly biased toward cytosine to thymine or the complement, and further partitioning loci by substitution type had a strong effect on Nb estimates. Minor allele frequency and base quality bias thresholds also had strong effects on Nb estimates. Instability of Nb with respect to common data filtering parameters and empirically identified factors prevented robust comparison of the two cohorts. Given that confidence intervals frequently included infinity as the stringency of data filtering increased, contemporary trends in Nb of North American hoary bats may not be tractable with the linkage disequilibrium method, at least using the protocol employed here.

Population structure of the Sahiwal breed in Pakistan

1995 ◽  
Vol 60 (2) ◽  
pp. 163-168 ◽  
Author(s):  
A. Dahlin ◽  
U. N. Khan ◽  
A. H. Zafar ◽  
M. Saleem ◽  
M. A. Chaudhry ◽  
...  
Keyword(s):  
Population Structure ◽  
Population Size ◽  
Effective Population Size ◽  
Breeding Population ◽  
Effective Population ◽  
Data Set ◽  
Inbreeding Coefficients ◽  
Sahiwal Cows ◽  
The Mean ◽  
Average Population Size

AbstractThe present study was undertaken to assist conservation and improvement schemes in the Sahiwal breed of cattle in Pakistan. A data set, consisting of records of 244 pure Sahiwal breeding bulls and 5247 cows, the latter representing about 80% of all recorded Sahiwal cows in Pakistan born during a period covering about 20 years, was analysed with regard to inbreeding, additive relationships, effective population size and generation intervals. Average inbreeding coefficients of 1224 cows and 49 bulls, for which at least the grandparents and great-grandsires were known, were 0·043 and 0·046, respectively. About two-thirds of the inbreeding was due to matings between animals with parents or grandparents in common. The mean additive relationship among the cows was 0·062, with within-herd averages ranging from 0·087 to 0·358. The average population size in a subdata set of recorded Sahiwal cattle from 1980 to 1984 was 1612, whereas the most likely estimate of the effective population size was about 30 animals for the same active breeding population. The study indicated the immediate need for an active conservation programme whereby the Sahiwal subpopulations of India and Kenya also should be involved.

scholarly journals ANALYZING GENE-FREQUENCY DATA WHEN THE EFFECTIVE POPULATION SIZE IS FINITE

Genetics ◽  
1980 ◽  
Vol 95 (2) ◽  
pp. 489-502
Author(s):  
Susan R Wilson
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Genetic Model ◽  
Size Structure ◽  
Balancing Selection ◽  
General Situation ◽  
Frequency Data ◽  
Effective Population ◽  
Data Set ◽  
Experimental Procedure

ABSTRACT The statistical methods used by SCHAFFER, YARDLEY and ANDERSON (1977) and by GIBSON et al. (1979) to analyze the variation in allele frequencies in two common types of experimental procedure, where the effective population size is finite, are extended to a more general situation involving a greater range of experiments. The analysis developed is more sensitive in detecting changes in allele frequency due to both fluctuating and balancing selection, as well as to directional selection. The error involved in many studies due to ignoring the effective population size structure would appear to be large. The range of hypotheses that can be considered may be increased as well. Finally, the method of determining bounds for the effective population size, when a particular genetic model is known to hold for a data set, is also outlined.

scholarly journals Whole genome linkage disequilibrium and effective population size in a coho salmon (Oncorhynchus kisutch) breeding population

2018 ◽  
Author(s):  
Agustín Barría ◽  
Kris A. Christensen ◽  
Grazyella Yoshida ◽  
Ana Jedlicki ◽  
Jean P. Lhorente ◽  
...  
Keyword(s):  
Linkage Disequilibrium ◽  
Population Size ◽  
Effective Population Size ◽  
Coho Salmon ◽  
Association Studies ◽  
Breeding Population ◽  
Physical Distance ◽  
Average Density ◽  
Whole Genome ◽  
Effective Population

AbstractThe estimation of linkage disequilibrium between molecular markers within a population is critical when establishing the minimum number of markers required for association studies, genomic selection and for inferring historical events influencing different populations. This work aimed to evaluate the extent and decay of linkage disequilibrium in a coho salmon breeding population using ddRAD genomic markers.Linkage disequilibrium was estimated between a total of 7,505 SNPs found in 62 individuals (33 dams and 29 sires) from the breeding population. The makers encompass all 30 coho salmon chromosomes and comprise 1,655.19 Mb of the genome. The average density of markers per chromosome ranged from 3.45 to 6.11 per 1 Mbp. The minor allele frequency averaged 0.20 (with a range from 0.08 to 0.50). The overall average linkage disequilibrium among SNPs pairs measured as r2 was 0.054. The Average r2 value decreased with increasing physical distance, with values ranging from 0.37 to 0.054 at distances lower than 1 kb and up to 10 Mb, respectively. An r2 threshold of 0.1 was reached at distance of approximately 1.3 Mb. Chromosomes Okis05, Okis15 and Okis28 showed high levels of linkage disequilibrium (> 0.20 at distances lower than 1 Mb). Average r2 values were lower than 0.1 for all chromosomes at distances greater than 4 Mb. Linkage disequilibrium values suggest that whole genome association and selection studies could be performed using about 75,000 SNPs in aquaculture populations (depending on the trait under investigation). From the identified SNPs, an effective population size of 100 was estimated for the population 10 generation ago, and 1,000, for 139 generations ago.Based on the extent of r2 decay, we suggest that at least 75,000 SNPs would be necessary for an association mapping study. Over 100,000 SNPs would be necessary for a high power study, in the current coho salmon population.

The broad-snouted caiman population recovery in Argentina. A case of genetics conservation

2017 ◽  
Vol 38 (4) ◽  
pp. 411-424 ◽  
Author(s):  
Patricia Susana Amavet ◽  
Eva Carolina Rueda ◽  
Juan César Vilardi ◽  
Pablo Siroski ◽  
Alejandro Larriera ◽  
...  
Keyword(s):  
Genetic Variability ◽  
Population Size ◽  
Effective Population Size ◽  
Population Genetic ◽  
Genetic Parameters ◽  
Population Recovery ◽  
Santa Fe ◽  
Effective Population ◽  
Population Genetic Parameters ◽  
The Impact

Caiman latirostriswild populations have suffered a drastic reduction in the past, and for that reason, a management and monitoring plan was applied since 1990 in Santa Fe, Argentina in order to achieve population recovery. Although ranching system has a noteworthy success in terms of population size recovering, there is no information about the estimation of population genetic parameters. In particular, the consequence of the bottleneck underwent by these populations has not been assessed. We evaluated variability and genetic structure ofC. latirostrispopulations from Santa Fe through time, using microsatellites and mitochondrial DNA. Population genetic parameters were compared among four sites and three different periods to assess the impact of management activities, and effective population size was estimated in order to detect bottleneck events. We observed an increase in microsatellite variability and low genetic variability in mitochondrial lineages through time. Variability estimates are similar among sites in each sampling period; and there is scarce differentiation among them. The genetic background of each sampling site has changed through time; we assume this fact may be due to entry of individuals of different origin, through management and repopulation activities. Moreover, taking into account the expected heterozygosity and effective population size values, it can be assumed that bottleneck events indeed have occurred in the recent past. Our results suggest that, in addition to increasing population size, genetic variability of the species has been maintained. However, the information is still incomplete, and regular monitoring should continue in order to arrive to solid conclusions.

scholarly journals SNP-based analysis reveals unexpected features of genetic diversity, parental contributions and pollen contamination in a white spruce breeding program

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Esteban Galeano ◽  
Jean Bousquet ◽  
Barb R. Thomas
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Effective Population Size ◽  
White Spruce ◽  
Seed Orchard ◽  
Pedigree Reconstruction ◽  
Effective Population ◽  
Pollen Contamination ◽  
Contamination Levels ◽  
The Impact

AbstractAccurate monitoring of genetic diversity levels of seedlots and mating patterns of parents from seed orchards are crucial to ensure that tree breeding programs are long-lasting and will deliver anticipated genetic gains. We used SNP genotyping to characterize founder trees, five bulk seed orchard seedlots, and trees from progeny trials to assess pollen contamination and the impact of severe roguing on genetic diversity and parental contributions in a first-generation open-pollinated white spruce clonal seed orchard. After severe roguing (eliminating 65% of the seed orchard trees), we found a slight reduction in the Shannon Index and a slightly negative inbreeding coefficient, but a sharp decrease in effective population size (eightfold) concomitant with sharp increase in coancestry (eightfold). Pedigree reconstruction showed unequal parental contributions across years with pollen contamination levels between 12 and 51% (average 27%) among seedlots, and 7–68% (average 30%) among individual genotypes within a seedlot. These contamination levels were not correlated with estimates obtained using pollen flight traps. Levels of pollen contamination also showed a Pearson’s correlation of 0.92 with wind direction, likely from a pollen source 1 km away from the orchard under study. The achievement of 5% genetic gain in height at rotation through eliminating two-thirds of the orchard thus generated a loss in genetic diversity as determined by the reduction in effective population size. The use of genomic profiles revealed the considerable impact of roguing on genetic diversity, and pedigree reconstruction of full-sib families showed the unanticipated impact of pollen contamination from a previously unconsidered source.

scholarly journals Transition densities and sample frequency spectra of diffusion processes with selection and variable population size

2015 ◽  
Author(s):  
Daniel Zivkovic ◽  
Matthias Steinrücken ◽  
Yun S. Song ◽  
Wolfgang Stephan
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Diffusion Processes ◽  
Transition Density ◽  
Effective Population ◽  
Frequency Spectra ◽  
Transition Densities ◽  
Population Sizes ◽  
Sample Frequency ◽  
The Impact

Advances in empirical population genetics have made apparent the need for models that simultaneously account for selection and demography. To address this need, we here study the Wright-Fisher diffusion under selection and variable effective population size. In the case of genic selection and piecewise-constant effective population sizes, we obtain the transition density function by extending a recently developed method for computing an accurate spectral representation for a constant population size. Utilizing this extension, we show how to compute the sample frequency spectrum (SFS) in the presence of genic selection and an arbitrary number of instantaneous changes in the effective population size. We also develop an alternate, efficient algorithm for computing the SFS using a method of moments. We apply these methods to answer the following questions: If neutrality is incorrectly assumed when there is selection, what effects does it have on demographic parameter estimation? Can the impact of negative selection be observed in populations that undergo strong exponential growth?

scholarly journals Impact of fertility variation on genetic diversity and phenotypic traits in second generation seed production areas and clonal seed orchards of Eucalyptus camaldulensis

2019 ◽  
Vol 68 (1) ◽  
pp. 29-40
Author(s):  
P.G. Suraj ◽  
K. Nagabhushana ◽  
R. Kamalakannan ◽  
M. Varghese
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Effective Population Size ◽  
Second Generation ◽  
Gene Diversity ◽  
Eucalyptus Camaldulensis ◽  
Phenotypic Traits ◽  
Effective Population ◽  
Fertility Variation ◽  
The Impact

Abstract Fertility and gene diversity were estimated in three second generation (F2) seed stands (SPA 1-3) and two clone trials (CSO 1&2) of Eucalyptus camaldulensis to assess the impact on seed crop. F2 seedlots were evaluated in comparison to native provenances, ten commercial clones and interspecific hybrids at diverse sites. SPA 1&2 were genetic gain trials of five first generation (F1) orchard seedlots, SPA 3 a plantation of one F1 orchard seedlot, and CSOs were clone trials of 21 commercial clones established at two contrasting sites. Fertility variation, as indicated by sibling coefficient, was high (Ψ, 9-14) in the SPAs as only about 26 % trees were fertile compared to 81 % trees in CSOs. Effective population size was higher in SPA 1 and 2 (Ns, 95 and 74, respectively) than SPA 3 (Ns = 39). Fertility was highly skewed in CSO 2 resulting in low effective population size (Ns = 2) compared to CSO 1 (Ns = 11). Constant seed collection enabled 3-fold increase in relative population size and 22 % higher predicted gene diversity in CSO 2. Genetic diversity (He) estimated using SSR markers was higher in SPA 1&2 and native provenances (NAT), compared to SPA 3 and CSO 1, whereas CSO 2 and clones had lower values. There was a high positive correlation between estimated He and predicted gene diversity values of SPAs and CSOs. He was positively correlated to mean field survival and negatively correlated to kraft pulp yield (KPY), evaluated at three years in progeny trials across three locations. Number of alleles per locus was higher in SPAs and native provenances compared to CSOs and clones. Discriminant principal component analysis clustered CSO, NAT and SPA seedlots in different groups while commercial E. camaldulensis clones clustered close to NAT. Multilocus outcrossing rate was generally high (tm, 91-100 %), though selfing was observed in two families of SPA 3 and CSO 2. Selected interspecific hybrid families of commercial E. camaldulensis clones (with E. urophylla and E. pellita) evaluated at two of the sites had higher He and KPY than clones at three years.

scholarly journals Palliating the impact of fixation of a major gene on the genetic variation of artificially selected polygenes

2006 ◽  
Vol 88 (2) ◽  
pp. 105-118 ◽  
Author(s):  
LEOPOLDO SÁNCHEZ ◽  
ARMANDO CABALLERO ◽  
ENRIQUE SANTIAGO
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Selective Sweep ◽  
Major Gene ◽  
Optimal Path ◽  
Fixation Time ◽  
Selection Intensity ◽  
Effective Population ◽  
The Impact ◽  
Polygenic Variation

Selective sweeps of variation caused by fixation of major genes may have a dramatic impact on the genetic gain from background polygenic variation, particularly in the genome regions closely linked to the major gene. The response to selection can be restrained because of the reduced selection intensity and the reduced effective population size caused by the increase in frequency of the major gene. In the context of a selected population where fixation of a known major gene is desired, the question arises as to which is the optimal path of increase in frequency of the gene so that the selective sweep of variation resulting from its fixation is minimized. Using basic theoretical arguments we propose a frequency path that maximizes simultaneously the effective population size applicable to the selected background and the selection intensity on the polygenic variation by minimizing the average squared selection intensity on the major gene over generations up to a given fixation time. We also propose the use of mating between carriers and non-carriers of the major gene, in order to promote the effective recombination between the major gene and its linked polygenic background. Using a locus-based computer simulation assuming different degrees of linkage, we show that the path proposed is more effective than a similar path recently published, and that the combination of the selection and mating methods provides an efficient way to palliate the negative effects of a selective sweep.

scholarly journals A pseudo-likelihood method for estimating effective population size from temporally spaced samples

2001 ◽  
Vol 78 (3) ◽  
pp. 243-257 ◽  
Author(s):  
JINLIANG WANG
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Growth Parameters ◽  
Computing Time ◽  
Likelihood Method ◽  
Effective Population ◽  
Data Set ◽  
Statistic Method ◽  
Pseudo Likelihood ◽  
Wide Range

A pseudo maximum likelihood method is proposed to estimate effective population size (Ne) using temporal changes in allele frequencies at multi-allelic loci. The computation is simplified dramatically by (1) approximating the multi-dimensional joint probabilities of all the data by the product of marginal probabilities (hence the name pseudo-likelihood), (2) exploiting the special properties of transition matrix and (3) using a hidden Markov chain algorithm. Simulations show that the pseudo-likelihood method has a similar performance but needs much less computing time and storage compared with the full likelihood method in the case of 3 alleles per locus. Due to computational developments, I was able to assess the performance of the pseudo-likelihood method against the F-statistic method over a wide range of parameters by extensive simulations. It is shown that the pseudo-likelihood method gives more accurate and precise estimates of Ne than the F-statistic method, and the performance difference is mainly due to the presence of rare alleles in the samples. The pseudo-likelihood method is also flexible and can use three or more temporal samples simultaneously to estimate satisfactorily the Nes of each period, or the growth parameters of the population. The accuracy and precision of both methods depend on the ratio of the product of sample size and the number of generations involved to Ne, and the number of independent alleles used. In an application of the pseudo-likelihood method to a large data set of an olive fly population, more precise estimates of Ne are obtained than those from the F-statistic method.

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