On the Potential for Estimating the Effective Number of Breeders From Heterozygote-Excess in Progeny

Genetics ◽  
1996 ◽  
Vol 144 (1) ◽  
pp. 383-387 ◽  
Author(s):  
A I Pudovkin ◽  
D V Zaykin ◽  
D Hedgecock
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Sampling Error ◽  
Demographic Data ◽  
Rank Correlation ◽  
Effective Number ◽  
Effective Population ◽  
Heterozygote Excess ◽  
Effective Number Of Breeders ◽  
Age Structured

Abstract The important parameter of effective population size is rarely estimable directly from demographic data. Indirect estimates of effective population size may be made from genetic data such as temporal variation of allelic frequencies or linkage disequilibrium in cohorts. We suggest here that an indirect estimate of the effective number of breeders might be based on the excess of heterozygosity expected in a cohort of progeny produced by a limited number of males and females. In computer simulations, heterozygote excesses for 30 unlinked loci having various numbers of alleles and allele-frequency profiles were obtained for cohorts produced by samples of breeders drawn from an age-structured population and having known variance in reproductive success and effective number. The 95% confidence limits around the estimate contained the true effective population size in 70 of 72 trials and the Spearman rank correlation of estimated and actual values was 0.991. An estimate based on heterozygote excess might have certain advantages over the previous estimates, requiring only single-locus and single-cohort data, but the sampling error among individuals and the effect of departures from random union of gametes still need-to be explored.

scholarly journals Evaluation of genetic effects on wild salmon populations from stock enhancement

2020 ◽  
Author(s):  
Ingerid J Hagen ◽  
Ola Ugedal ◽  
Arne J Jensen ◽  
Håvard Lo ◽  
Espen Holthe ◽  
...  
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Salmo Salar ◽  
Conservation Value ◽  
Effective Number ◽  
Effective Population ◽  
Wild Salmon ◽  
Effective Number Of Breeders ◽  
Additional Strain ◽  
Conservation Concern

Abstract Many salmonid populations are of conservation concern, and the release of hatchery-produced juveniles is a frequently used measure to alleviate declines and increase harvest opportunities. While such releases may be of conservation value for some populations, stocking may also decrease the effective population size and subsequently impose additional strain on already threatened populations. In this study, we assessed how the cohort-wise effective number of breeders in five populations of Atlantic salmon (Salmo salar) were affected by supplementation. Altogether, 19 cohorts were studied (2–7 cohorts per population) by estimating the proportion hatchery-released individuals and the effective number of wild and captive breeders in each cohort of the respective populations. We show that the effect of releasing captive-bred individuals varies both between populations and between years within the same population. A Ryman–Laikre effect—where the effective number of breeders has decreased as a consequence of supplementation—was observed for 11 cohorts. We discuss how supplementation can be adapted to optimize the effective population size, demonstrate that evaluation of supplementation can be reliably achieved, and show that supplementation programmes that lead to high proportions of hatchery-origin fish on spawning grounds are more likely to induce a Ryman–Laikre effect.

scholarly journals Interrelations between effective population size and other pedigree tools for the management of conserved populations

2000 ◽  
Vol 75 (3) ◽  
pp. 331-343 ◽  
Author(s):  
ARMANDO CABALLERO ◽  
MIGUEL A. TORO
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Population Size ◽  
Effective Population Size ◽  
Genetic Parameters ◽  
Effective Number ◽  
Effective Population ◽  
Clear Cut ◽  
Captive Populations ◽  
Practical Recommendations

Genetic parameters widely used to monitor genetic variation in conservation programmes, such as effective number of founders, founder genome equivalents and effective population size, are interrelated in terms of coancestries and variances of contributions from ancestors to descendants. A new parameter, the effective number of non-founders, is introduced to describe the relation between effective number of founders and founder genome equivalents. Practical recommendations for the maintenance of genetic variation in small captive populations are discussed. To maintain genetic diversity, minimum coancestry among individuals should be sought. This minimizes the variances of contributions from ancestors to descendants in all previous generations. The method of choice of parents and the system of mating should be independent of each other because a clear-cut recommendation cannot be given on the latter.

scholarly journals A method to estimate effective population size from linkage disequilibrium when generations overlap

2021 ◽  
Author(s):  
Luis Alberto García Cortés ◽  
Frédéric Austerlitz ◽  
M. Ángeles R. de Cara
Keyword(s):  
Linkage Disequilibrium ◽  
Population Size ◽  
Effective Population Size ◽  
Age Groups ◽  
Cohort Size ◽  
Effective Population ◽  
Zonotrichia Leucophrys ◽  
Age Structured ◽  
Made In ◽  
Key Parameter

AbstractEffective population size (Ne) is a key parameter in evolutionary and conservation studies. It characterises the number of unique or distinct individuals in a population, and can be used to establish management programmes. Several methods have been developed to estimate this parameter. Currently, for studies with one sample in time, the simplest methods are based on linkage disequilibrium. These methods rely on simple models, and biases have been shown when populations deviate from the assumptions made in those models. This occurs in particular when populations are age-structured or have overlapping generations. Recently, several methods have been developed to correct such biases. Here, we develop analytical equations to predict linkage disequilibrium within age groups, and use such results to infer cohort size from samples of newborn individuals. We can in turn use these equations to estimate Ne accurately for a variety of species. Furthermore, using publicly available data, we apply our method to the white-crowned sparrow (Zonotrichia leucophrys).

scholarly journals Genetic diversity, viability and conservation value of the global captive population of the Moroccan Royal lions

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0258714
Author(s):  
Kristina Lehocká ◽  
Simon A. Black ◽  
Adrian Harland ◽  
Ondrej Kadlečík ◽  
Radovan Kasarda ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Effective Population Size ◽  
North Africa ◽  
Reference Population ◽  
Captive Population ◽  
Effective Number ◽  
Pedigree Data ◽  
Effective Population ◽  
Loss Of Diversity

This study evaluates the diversity of the so-called ‘Moroccan Royal lions’ using genealogical information. Lions are no longer extant in North Africa, but the previous wild population was an important element of the now-recognised northern subspecies (Panthera leo leo) that ranged across West Africa, North Africa and the Middle East into India. The remaining captive population of ‘Moroccan Royal lions’ seems to be significantly endangered by the loss of diversity due to the effective population size decrease. The pedigree file of this captive lion population consisted of 454 individuals, while the reference population included 98 animals (47 males and 51 females). The completeness of the pedigree data significantly decreased with an increasing number of generations. The highest percentage of pedigree completeness (over 70%) was achieved in the first generation of the reference population. Pedigree-based parameters derived from the common ancestor and gene origin were used to estimate the state of diversity. In the reference population, the average inbreeding coefficient was 2.14%, while the individual increase in inbreeding over generations was 2.31%. Overall, the reference population showed lower average inbreeding and average relatedness compared with the pedigree file. The number of founders (47), the effective number of founders (24) and the effective number of ancestors (22) were estimated in the reference population. The effective population size of 14.02 individuals confirms the critically endangered status of the population and rapid loss of diversity in the future. Thus, continuous monitoring of the genetic diversity of the ‘Moroccan Royal lion’ group is required, especially for long-term conservation management purposes, as it would be an important captive group should further DNA studies establish an affinity to P. leo leo.

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