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Related Concept Videos

Types of Selection01:46

Types of Selection

Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...
Frequency-dependent Selection01:21

Frequency-dependent Selection

When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.
Regression Toward the Mean01:52

Regression Toward the Mean

Regression toward the mean (“RTM”) is a phenomenon in which extremely high or low values—for example, and individual’s blood pressure at a particular moment—appear closer to a group’s average upon remeasuring. Although this statistical peculiarity is the result of random error and chance, it has been problematic across various medical, scientific, financial and psychological applications. In particular, RTM, if not taken into account, can interfere when researchers try to extrapolate results...
Longitudinal Research02:20

Longitudinal Research

Sometimes we want to see how people change over time, as in studies of human development and lifespan. When we test the same group of individuals repeatedly over an extended period of time, we are conducting longitudinal research. Longitudinal research is a research design in which data-gathering is administered repeatedly over an extended period of time. For example, we may survey a group of individuals about their dietary habits at age 20, retest them a decade later at age 30, and then again...
Hardy-Weinberg Principle01:49

Hardy-Weinberg Principle

Diploid organisms have two alleles of each gene, one from each parent, in their somatic cells. Therefore, each individual contributes two alleles to the gene pool of the population. The gene pool of a population is the sum of every allele of all genes within that population and has some degree of variation. Genetic variation is typically expressed as a relative frequency, which is the percentage of the total population that has a given allele, genotype or phenotype.
Longitudinal Studies01:26

Longitudinal Studies

Longitudinal studies are also widely used in other medical and social science fields. For instance, in cardiovascular research, they can monitor patients' health over decades to identify risk factors for heart disease, such as high cholesterol or smoking, and evaluate the long-term effectiveness of preventive measures. Similarly, in mental health studies, researchers might follow individuals from adolescence into adulthood to understand the development and progression of conditions like...

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Related Experiment Video

Updated: May 25, 2026

Genome-wide Determination of Mammalian Replication Timing by DNA Content Measurement
08:06

Genome-wide Determination of Mammalian Replication Timing by DNA Content Measurement

Published on: January 19, 2017

Directional selection in temporally replicated studies is remarkably consistent.

Michael B Morrissey1, Jarrod D Hadfield

  • 1Institute of Evolutionary Biology, University of Edinburgh, The King's Buildings, Edinburgh EH9 3JT, Scotland. michael.morrissey@ed.ac.uk

Evolution; International Journal of Organic Evolution
|January 27, 2012
PubMed
Summary
This summary is machine-generated.

Directional selection in nature appears remarkably constant over time. New analysis reveals that apparent temporal variation in evolutionary selection is often an artifact of statistical sampling error, not real biological change.

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Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization
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Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

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17:14

Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

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Area of Science:

  • Evolutionary Biology
  • Population Genetics
  • Quantitative Genetics

Background:

  • Temporal variation in selection is a key factor influencing evolutionary trajectories in natural populations.
  • Previous synthetic analyses suggested substantial temporal heterogeneity in the strength and direction of natural selection.
  • Acknowledged limitations in prior studies included the potential inflation of variation estimates due to sampling error.

Purpose of the Study:

  • To reanalyze existing data on temporal variation in selection, explicitly accounting for the influence of sampling error.
  • To determine if directional selection in natural populations exhibits genuine temporal heterogeneity or if observed variation is an artifact.

Main Methods:

  • Utilized statistical techniques designed to differentiate true biological variation from variation introduced by sampling error.
  • Reanalyzed a synthetic dataset from a previous study on temporal variation in selection.
  • Focused on estimating parameters of the distribution of selection, rather than parameters of the distribution of estimated selection.

Main Results:

  • After accounting for sampling error, directional selection was found to be remarkably constant in both magnitude and direction over time.
  • The study demonstrates that much of the previously reported temporal heterogeneity in selection may be an artifact of statistical methods.
  • The findings challenge the conclusion of substantial temporal heterogeneity in selection based on the reanalyzed dataset.

Conclusions:

  • The available data do not support the existence of substantial temporal heterogeneity in directional selection.
  • Emphasizes the critical importance of employing statistical methods that correct for sampling error when assessing temporal variation in selection.
  • Misinterpretations can arise from focusing on the distribution of estimated selection rather than the true distribution of selection parameters.