Related Experiment Video
Updated: Aug 2, 2025
Establishment of Viral Infection and Analysis of Host-Virus Interaction in Drosophila Melanogaster
Published on: March 14, 2019
Limited host availability disrupts the genetic correlation between virulence and transmission
Diogo P Godinho1, Leonor R Rodrigues1, Sophie Lefèvre2
1cE3c: Centre for Ecology, Evolution, and Environmental Changes, Faculty of Sciences, University of Lisbon, Lisboa, Portugal.
Abstract:
Virulence is expected to be linked to parasite fitness via transmission. However, it is not clear whether this relationship is genetically determined, nor if it differs when transmission occurs continuously during, or only at the end of, the infection period. Here, we used inbred lines of the macroparasitic spider mite Tetranychus urticae to disentangle genetic vs. nongenetic correlations among traits, while varying parasite density and opportunities for transmission. A positive genetic correlation between virulence and the number of transmitting stages produced was found under continuous transmission. However, if transmission occurred only at the end of the infection period, this genetic correlation disappeared. Instead, we observed a negative relationship between virulence and the number of transmitting stages, driven by density dependence. Thus, within-host density dependence caused by reduced opportunities for transmission may hamper selection for higher virulence, providing a novel explanation as to why limited host availability leads to lower virulence.
Insights
Parasite virulence and transmission are linked, but genetics matter. Continuous transmission showed a positive genetic link, while end-of-infection transmission revealed density dependence reducing virulence.
Area of Science:
- Evolutionary biology
- Parasitology
- Ecology
Background:
- Virulence is often linked to parasite fitness through transmission.
- The genetic basis of this relationship and its dependence on transmission timing remain unclear.
Purpose of the Study:
- To investigate the genetic basis of the virulence-transmission relationship in Tetranychus urticae.
- To determine how transmission opportunities (continuous vs. end-of-infection) affect this relationship.
Main Methods:
- Utilized inbred lines of the spider mite Tetranychus urticae.
- Manipulated parasite density and transmission timing.
- Assessed genetic and nongenetic correlations between virulence and transmission traits.
Main Results:
- A positive genetic correlation between virulence and transmitting stages was observed under continuous transmission.
- This genetic correlation disappeared under end-of-infection transmission.
- Density dependence led to a negative relationship between virulence and transmitting stages when transmission was limited.
Conclusions:
- Within-host density dependence can limit selection for increased virulence when transmission opportunities are reduced.
- Limited host availability may consequently lead to lower parasite virulence.
- Genetic and environmental factors interact to shape the evolution of virulence.
Related Concept Videos
01:09Mutation, Gene Flow, and Genetic Drift
01:26Factors Affecting the Risk of Infection
The integrity and count of the white blood cells help the body resist pathogens and fight infection. When impaired, it reduces the body's resistance to pathogens. The acidic pH levels of the gastrointestinal, genitourinary tracts, and skin...
02:39Gene Flow
02:18Types of Genetic Transfer Between Organisms
01:20Infection
The chain begins with pathogens: bacteria, viruses, fungi, prions, or parasites such as protozoa helminths. These can be present on the skin as transient or resident flora, or they can be acquired from the environment. Identifying and treating the type of infection and...