Sewall Wright: Chance and Evolution in Small Populations

The harmful impacts of inbreeding are generally greater in species that naturally outbreed compared to those in inbreeding species, greater in stressful than benign environments, greater for fitness than peripheral traits, and greater for total fitness compared to its individual components. Inbreeding reduces survival and reproduction (i.e., it causes inbreeding depression), and thereby increases the risk of extinction. Inbreeding depression is due to increased homozygosity for harmful alleles and at loci exhibiting heterozygote advantage. Natural selection may remove (purge) the alleles that cause inbreeding depression, especially following inbreeding or population bottlenecks, but it has limited effects in small populations and usually does not completely eliminate inbreeding depression. Inbreeding depression is nearly universal in sexually reproducing organisms that are diploid or have higher ploidies.

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Evolutionary genetics of small populations

10.1093/oso/9780198783398.003.0002 ◽

2017 ◽

Author(s):

Richard Frankham ◽

Jonathan D. Ballou ◽

Katherine Ralls ◽

Mark D. B. Eldridge ◽

Michele R. Dudash ◽

...

Keyword(s):

Genetic Diversity ◽

Population Size ◽

Evolutionary Genetics ◽

Small Population ◽

Small Populations ◽

Effective Population ◽

Genetic Management ◽

Evolutionary Genetic ◽

Loss Of Genetic Diversity ◽

Number Of Individuals

Genetic management of fragmented populations involves the application of evolutionary genetic theory and knowledge to alleviate problems due to inbreeding and loss of genetic diversity in small population fragments. Populations evolve through the effects of mutation, natural selection, chance (genetic drift) and gene flow (migration). Large outbreeding, sexually reproducing populations typically contain substantial genetic diversity, while small populations typically contain reduced levels. Genetic impacts of small population size on inbreeding, loss of genetic diversity and population differentiation are determined by the genetically effective population size, which is usually much smaller than the number of individuals.

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Small Populations, High-Dimensional Spaces: Sparse Covariance Matrix Adaptation

Proceedings of the 2015 Federated Conference on Computer Science and Information Systems ◽

10.15439/2015f261 ◽

2015 ◽

Cited By ~ 1

Author(s):

Silja Meyer-Nieberg ◽

Erik Kropat

Keyword(s):

Covariance Matrix ◽

High Dimensional ◽

Small Populations ◽

Covariance Matrix Adaptation

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Nature, Nurture, and Noise: Developmental Instability, Fluctuating Asymmetry, and the Causes of Phenotypic Variation

Symmetry ◽

10.3390/sym13071204 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1204

Author(s):

John H. Graham

Keyword(s):

Fluctuating Asymmetry ◽

Phenotypic Variation ◽

Deterministic Chaos ◽

Monozygotic Twins ◽

Developmental Instability ◽

Nonlinear Feedback ◽

Developmental Variation ◽

Sewall Wright ◽

Developmental Noise ◽

And Behavior

Phenotypic variation arises from genetic and environmental variation, as well as random aspects of development. The genetic (nature) and environmental (nurture) components of this variation have been appreciated since at least 1900. The random developmental component (noise) has taken longer for quantitative geneticists to appreciate. Here, I sketch the historical development of the concepts of random developmental noise and developmental instability, and its quantification via fluctuating asymmetry. The unsung pioneers in this story are Hugo DeVries (fluctuating variation, 1909), C. H. Danforth (random variation between monozygotic twins, 1919), and Sewall Wright (random developmental variation in piebald guinea pigs, 1920). The first pioneering study of fluctuating asymmetry, by Sumner and Huestis in 1921, is seldom mentioned, possibly because it failed to connect the observed random asymmetry with random developmental variation. This early work was then synthesized by Boris Astaurov in 1930 and Wilhelm Ludwig in 1932, and then popularized by Drosophila geneticists beginning with Kenneth Mather in 1953. Population phenogeneticists are still trying to understand the origins and behavior of random developmental variation. Some of the developmental noise represents true stochastic behavior of molecules and cells, while some represents deterministic chaos, nonlinear feedback, and symmetry breaking.

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Vital rates of two small populations of brown bears in Canada and range‐wide relationship between population size and trend

Ecology and Evolution ◽

10.1002/ece3.7301 ◽

2021 ◽

Vol 11 (7) ◽

pp. 3422-3434

Author(s):

Michelle L. McLellan ◽

Bruce N. McLellan ◽

Rahel Sollmann ◽

Heiko U. Wittmer

Keyword(s):

Population Size ◽

Small Populations ◽

Vital Rates ◽

Brown Bears

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Recombination Can Evolve in Large Finite Populations Given Selection on Sufficient Loci

Genetics ◽

10.1093/genetics/165.4.2249 ◽

2003 ◽

Vol 165 (4) ◽

pp. 2249-2258 ◽

Cited By ~ 9

Author(s):

Mark M Iles ◽

Kevin Walters ◽

Chris Cannings

Keyword(s):

Experimental Evidence ◽

Genetic Drift ◽

Finite Population ◽

Selective Advantage ◽

Indirect Selection ◽

Small Populations ◽

Finite Populations ◽

Population Sizes ◽

Population Recombination

AbstractIt is well known that an allele causing increased recombination is expected to proliferate as a result of genetic drift in a finite population undergoing selection, without requiring other mechanisms. This is supported by recent simulations apparently demonstrating that, in small populations, drift is more important than epistasis in increasing recombination, with this effect disappearing in larger finite populations. However, recent experimental evidence finds a greater advantage for recombination in larger populations. These results are reconciled by demonstrating through simulation without epistasis that for m loci recombination has an appreciable selective advantage over a range of population sizes (am, bm). bm increases steadily with m while am remains fairly static. Thus, however large the finite population, if selection acts on sufficiently many loci, an allele that increases recombination is selected for. We show that as selection acts on our finite population, recombination increases the variance in expected log fitness, causing indirect selection on a recombination-modifying locus. This effect is enhanced in those populations with more loci because the variance in phenotypic fitnesses in relation to the possible range will be smaller. Thus fixation of a particular haplotype is less likely to occur, increasing the advantage of recombination.

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Recent Invasion of the Endemic Banggai Cardinalfish, Pterapogon kauderni at The Strait of Bali: Assessment of the Habitat Type and Population Structure

ILMU KELAUTAN Indonesian Journal of Marine Sciences ◽

10.14710/ik.ijms.24.1.15-22 ◽

2019 ◽

Vol 24 (1) ◽

pp. 15 ◽

Cited By ~ 1

Author(s):

I Nyoman Giri Putra ◽

I Dewa Nyoman Nurweda Putra

Keyword(s):

Natural Habitat ◽

Habitat Type ◽

Marine Organisms ◽

Aquarium Trade ◽

Small Populations ◽

Depth Range ◽

Habitat Types ◽

Weight Relationship ◽

Narrow Bay ◽

Sexually Mature

The demands of marine organisms for the aquarium trade are remain high and seems continue to increase. Consequently, many of marine organisms has been spread out from its natural habitat as in the case of endemic Banggai cardinalfish, (Pterapogon kauderni). That has invaded “new” habitat since it being trade in 1995. In recent years, a small populations of P. kauderni is known to be exist in a narrow bay near the Gilimanuk harbor, Bali. An underwater visual fish census survey was conducted on June 2018 to estimate the habitat types and densities of P. kauderni. Additionally, 23 specimens of P. kauderni were collected randomly in order to assess biological parameters such as the length-weight relationship. We successfully recorded 30 groups of P. kauderni that inhabit a shallow areas with a depth range between 0.5m to 2m. Of these, more than 90% of the groups were found to be associated with sea urchin (Diadema sp.) while the rest were found to live together with branching coral (Acropora sp.) and branching sponge (Ptylocaulis sp.). Total number of fish observed during the survey were 381 individuals. The fish density is 0.76 individu.m-2. Length-weight relationship showed that P. kauderni exhibit is negative allometry (b<3) which mean that the increase in length is faster than the weight gain. Interestingly, from the 23 specimens collected, none of these were sexually mature (SL<41 mm) which may indicated that the population of P. kauderni in Bali are under serious threats of exploitation.

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