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Related Experiment Video

Updated: Jan 10, 2026

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Published on: February 3, 2023

Rapid evolution of a large structural polymorphism during a bacterial epidemic.

Eric Dexter^1,2, Pascal Angst³, Peter D Fields³

¹Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland. eric@dexter-analytics.com.

|November 25, 2025

Summary

Researchers discovered a large structural polymorphism in the Daphnia magna genome linked to immune function. One form strongly correlates with susceptibility to the bacterium Pasteuria ramosa, showing rapid selection during epidemics.

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Area of Science:

Genomics
Evolutionary Biology
Population Genetics

Background:

Population genetics traditionally focuses on simple genetic variants like SNPs, INDELs, and CNVs.
Advancements in sequencing technology are enabling the discovery of large-scale genomic variants.
Structural variations are increasingly recognized for their biological significance.

Purpose of the Study:

To investigate a large structural polymorphism in the Daphnia magna genome.
To determine the association of this polymorphism with immune function and parasite resistance.
To understand the evolutionary dynamics of this structural variation.

Main Methods:

Genome sequencing and analysis of Daphnia magna.
Identification and characterization of large structural polymorphisms (LSPs).
Association studies between LSPs and susceptibility to Pasteuria ramosa infection.

Main Results:

An unusually large (2-5 Mb) and highly variable structural feature, termed large structural polymorphism (LSP), was identified in the Daphnia magna genome.
One haplotype (LSP-5-1.1) was strongly correlated with susceptibility to the bacterium Pasteuria ramosa.
Rapid selection against the susceptible haplotype (LSP-5-1.1) was observed during a natural P. ramosa epidemic, leading to increased population-wide resistance.

Conclusions:

Large structural polymorphisms can play a significant role in immune function and adaptation.
The identified LSP in Daphnia magna is under strong selection pressure related to Pasteuria ramosa parasitism.
Evidence suggests balancing selection on this structural polymorphism, indicating complex evolutionary dynamics possibly involving counter-selection against resistance.