Effective population size/adult population size ratios in wildlife: a review

Frankham, Richard

doi:10.1017/s0016672300034455

Cited by 1,229 publications

(1,349 citation statements)

References 84 publications

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“…LDNe estimates effective population sizes excluding allele frequencies below the critical values of 0.05, 0.02, and 0.01 to assess the effects of rare alleles in the data. The ratio of the effective population size to the census size (Ne/N) can be used to predict inbreeding and genetic variation loss in wildlife populations (Frankham 1995).…”

Section: Discussionmentioning

confidence: 99%

“…The ratios of effective breeders to the estimated population sizes were determined to be 0.06 in Isabela and 0.03 in Liguasan Marsh. These estimates hover about the 0.05 ratio threshold which Frankham (1995) With only two extant populations of C. mindorensis known to remain today, it is imperative to evaluate the similarity or differences between the two. Biogeographic differences might exist since the Isabela population exists in the northern extreme of the distribution whereas the Liguasan Marsh population is found in the southern extreme.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Population genetics implications for the conservation of the Philippine Crocodile Crocodylus mindorensis Schmidt, 1935 (Crocodylia: Crocodylidae)

Hinlo¹,

Tabora²,

Bailey³

et al. 2014

J. Threat. Taxa

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Population genetics implications for the conservation of the Philippine Crocodile Crocodylus mindorensis Schmidt, 1935 (Crocodylia: Crocodylidae)

Hinlo¹,

Tabora²,

Bailey³

et al. 2014

J. Threat. Taxa

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“…N e is often much lower than census size (Frankham, 1995), demonstrating that simply counting individuals is insufficient to predict rates of evolutionary change. In addition to the number of mating individuals, N e is affected by sex ratio, variation in reproductive success, age structure, migration and other demographic factors.…”

Section: Introductionmentioning

confidence: 99%

“…Heredity (Wright, 1931), which determines the rate of evolutionary change due to genetic drift and informs the equilibrium level of genetic variation and the effectiveness of selection. N e is often much lower than census size (Frankham, 1995), demonstrating that simply counting individuals is insufficient to predict rates of evolutionary change. In addition to the number of mating individuals, N e is affected by sex ratio, variation in reproductive success, age structure, migration and other demographic factors.…”

mentioning

confidence: 99%

Estimating contemporary effective population size in non-model species using linkage disequilibrium across thousands of loci

2016

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Contemporary effective population size (N e ) can be estimated using linkage disequilibrium (LD) observed across pairs of loci presumed to be selectively neutral and unlinked. This method has been commonly applied to data sets containing 10-100 loci to inform conservation and study population demography. Performance of these N e estimates could be improved by incorporating data from thousands of loci. However, these thousands of loci exist on a limited number of chromosomes, ensuring that some fraction will be physically linked. Linked loci have elevated LD due to limited recombination, which if not accounted for can cause N e estimates to be downwardly biased. Here, we present results from coalescent and forward simulations designed to evaluate the bias of LD-based N e estimates (N e ). Contrary to common perceptions, increasing the number of loci does not increase the magnitude of linkage. Although we show it is possible to identify some pairs of loci that produce unusually large r 2 values, simply removing large r 2 values is not a reliable way to eliminate bias. Fortunately, the magnitude of bias inN e is strongly and negatively correlated with the process of recombination, including the number of chromosomes and their length, and this relationship provides a general way to adjust for bias. Additionally, we show that with thousands of loci, precision ofN e is much lower than expected based on the assumption that each pair of loci provides completely independent information. Heredity (Wright, 1931), which determines the rate of evolutionary change due to genetic drift and informs the equilibrium level of genetic variation and the effectiveness of selection. N e is often much lower than census size (Frankham, 1995), demonstrating that simply counting individuals is insufficient to predict rates of evolutionary change. In addition to the number of mating individuals, N e is affected by sex ratio, variation in reproductive success, age structure, migration and other demographic factors. It is an extremely relevant metric in conservation biology, with low N e leading to inbreeding and reduced genetic diversity (Ellstrand and Elam, 1993). See Charlesworth (2009) for a primer on N e , and Wang (2005) for a review of estimation methods.Populations with smaller N e undergo more genetic drift than larger populations. This genetic drift randomly generates associations between alleles at different loci, known as linkage (or gametic) disequilibrium (LD) at a rate inversely proportional to N e . As a result, measures of LD between independently-segregating loci can be used to provide an estimate of N e (Sved, 1971;Hill, 1981;Waples, 1991). Over the past decades, many studies have leveraged data sets consisting of a few dozen loci for genetic estimates of N e (Luikart et al., 2010). While these studies continue to be useful, especially for long-running

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“…Future climate change scenarios are predicted to increase these sex ratio biases, with implications for population viability [2,3,6,7]. Potential consequences include a reduction in effective population size (N e ) that will exacerbate the negative effects of inbreeding and increase genetic drift in small populations [8], the inability to find mates leading to reduced fecundity or female infertility [9], and, under more extreme climate projections, the production of single sex cohorts [3,7].…”

Section: Introductionmentioning

confidence: 99%

Turtle mating patterns buffer against disruptive effects of climate change

et al. 2012

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For organisms with temperature-dependent sex determination (TSD), skewed offspring sex ratios are common. However, climate warming poses the unique threat of producing extreme sex ratio biases that could ultimately lead to population extinctions. In marine turtles, highly female-skewed hatchling sex ratios already occur and predicted increases in global temperatures are expected to exacerbate this trend, unless species can adapt. However, it is not known whether offspring sex ratios persist into adulthood, or whether variation in male mating success intensifies the impact of a shortage of males on effective population size. Here, we use parentage analysis to show that in a rookery of the endangered green turtle (Chelonia mydas), despite an offspring sex ratio of 95 per cent females, there were at least 1.4 reproductive males to every breeding female. Our results suggest that male reproductive intervals may be shorter than the 2 -4 years typical for females, and/or that males move between aggregations of receptive females, an inference supported by our satellite tracking, which shows that male turtles may visit multiple rookeries. We suggest that male mating patterns have the potential to buffer the disruptive effects of climate change on marine turtle populations, many of which are already seriously threatened.

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Effective population size/adult population size ratios in wildlife: a review

Cited by 1,229 publications

References 84 publications

Population genetics implications for the conservation of the Philippine Crocodile Crocodylus mindorensis Schmidt, 1935 (Crocodylia: Crocodylidae)

Population genetics implications for the conservation of the Philippine Crocodile Crocodylus mindorensis Schmidt, 1935 (Crocodylia: Crocodylidae)

Estimating contemporary effective population size in non-model species using linkage disequilibrium across thousands of loci

Turtle mating patterns buffer against disruptive effects of climate change

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