Adaptive Landscape & de Finetti Diagram — 2D Heterozygote Advantage

What the Adaptive Landscape Is

The adaptive landscape is a conceptual tool used in evolutionary biology to visualize how different genotypes contribute to fitness. In this context, it represents the mean fitness of a population as a function of allele frequencies. The landscape peaks at the genotype combination that maximizes fitness under given selection pressures.

The 2D heterozygote-advantage adaptive landscape illustrates how heterozygotes (individuals with two different alleles) can have an advantage over homozygotes (individuals with two identical alleles), leading to a complex and dynamic fitness landscape.

Why the de Finetti Diagram Matters

The de Finetti diagram is a powerful tool in population genetics that provides a visual representation of genotype frequencies. It plots the probabilities of different genotypes against each other, allowing for a clear understanding of how these frequencies change over time under various selection pressures.

By comparing real sampled genotype frequencies to the Hardy-Weinberg equilibrium (a parabola representing expected frequencies in the absence of evolutionary forces), the de Finetti diagram helps us assess the impact of natural selection and genetic drift on population structure.

The Role of Selection Coefficients

Selection coefficients, denoted as s1 and s2, quantify the relative fitness of each homozygote genotype. These values determine how much more or less fit a particular genotype is compared to the average population. In this simulation, adjusting these coefficients allows you to explore different scenarios where one genotype may have an advantage over another.

Understanding selection coefficients is crucial for predicting evolutionary outcomes and identifying which genotypes are likely to become fixed in a population.

Deterministic vs. Stochastic Dynamics

The simulation includes both deterministic (no-drift) and stochastic (drift-spread band) models of population dynamics. The deterministic model provides a theoretical trajectory based on the mean fitness landscape, while the drift-spread band shows the variability in allele frequencies due to random genetic drift.

By comparing these two models, you can observe how much real-world population dynamics deviate from expected outcomes and gain insights into the role of chance in evolutionary processes.

Frequently asked questions

Try it live

Everything above runs in your browser — open Adaptive Landscape & de Finetti Diagram — 2D Heterozygote Advantage and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.