Related Experiment Video
Updated: Jul 10, 2026
10:00
Measurement of Lifespan in Drosophila melanogaster
Published on: January 7, 2013
Selection against demographic stochasticity in age-structured populations
1Department of Biological Sciences, University of Texas, El Paso, Texas 79968, USA. mshpak@utep.edu
Genetics
|October 20, 2007
Summary
Genotypes with lower variance in offspring number can invade populations, even with lower average fitness. This study extends this to age-structured populations, showing selection favors lower demographic variance.
Area of Science:
- Population Genetics
- Evolutionary Biology
- Mathematical Biology
Background:
- Fecundity variance influences genotype invasion probability in finite populations.
- Lower variance in offspring number can be advantageous even with lower mean fitness.
- Previous work by Gillespie and Engen provides foundational concepts.
Purpose of the Study:
- Extend Gillespie's fecundity variance findings to age-structured populations.
- Utilize demographic variance as a generalized measure for allele frequency dynamics.
- Investigate the interplay of deterministic selection and random genetic drift.
Main Methods:
- Calculated demographic variance from life-history parameters (age-specific survival and fertility).
- Derived a diffusion approximation for selection and drift in age-structured populations.
- Validated the model using individual-based simulations for two genotypes.
Main Results:
- Selection against demographic variance favors genotypes with lower stochasticity in life-history rates.
- The derived diffusion approximation aligns with simulation results.
- Perturbation analyses of mean and variance in growth rate are crucial for fitness sensitivity.
Conclusions:
- Demographic variance is a key factor in genotype invasion and evolution in age-structured populations.
- Selection can favor reduced stochasticity in life-history traits.
- Understanding both mean and variance of growth rate is essential for predicting evolutionary trajectories.
Related Concept Videos
01:16Stratified Sampling Method
Sampling is a technique to select a portion (or subset) of the larger population and study that portion (the sample) to gain information about the population. The sampling method ensures that samples are drawn without bias and accurately represent the population. Because measuring the entire population in a study is not practical, researchers use samples to represent the population of interest.
To choose a stratified sample, divide the population into groups called strata and then take a...
To choose a stratified sample, divide the population into groups called strata and then take a...
01:22Applications of Life Tables
Life tables are versatile across various fields, providing a quantitative basis for analyzing mortality and survival rates. Whether used by demographers, actuaries, epidemiologists, or sociologists, life tables offer valuable insights into the dynamics of life and death, facilitating informed decisions in public health, insurance, conservation, and beyond. Their broad applicability highlights the interconnectedness of demographic data with practical outcomes in everyday life and strategic...
03:33Genetic Drift
Natural selection—probably the most well-known evolutionary mechanism—increases the prevalence of traits that enhance survival and reproduction. However, evolution does not merely propagate favorable traits, nor does it always benefit populations.Life is not fair. A deer grazing contentedly in a field can have her meal cut tragically short by a bolt of lightning. If the doomed doe is one of only three in the population, 1/3 of the population’s gene pool is lost. Random events like this can...
01:29Life Histories
Constrained by limited energy and resources, organisms must compromise between offspring quantity and parental investment. This trade-off is represented by two primary reproductive strategies; K-strategists produce few offspring but provide substantial parental support, whereas r-strategists produce much progeny that receives little care. These strategies are related to an organism’s survival likelihood across its lifespan, which is represented by a survivorship curve. Three general types of...
01:21Frequency-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.Positive Frequency-Dependent SelectionIn positive...
00:57Population Growth
Population size is dynamic, increasing with birth rates and immigration, and decreasing with death rates and emigration. In ideal conditions with unlimited resources, populations can increase exponentially, which plots as a J-shaped growth rate curve of population size against time. This type of curve is characteristic of newly-introduced invasive species, or populations that have suffered catastrophic declines and are rebounding.However, realistic environmental conditions limit the number of...