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Related Experiment Video

Updated: Mar 1, 2026

Probing the Limits of Egg Recognition Using Egg Rejection Experiments Along Phenotypic Gradients

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Published on: August 22, 2018

SELECTION OF BENEVOLENCE IN A HOST-PARASITE SYSTEM.

J J Bull¹, Ian J Molineux², W R Rice³

¹Department of Zoology, University of Texas, Austin, TX, 78712, USA.

Evolution; International Journal of Organic Evolution

|June 1, 2017

Summary

Parasite transmission mode critically impacts cooperation evolution. Vertical transmission favors benevolent parasite strains, while horizontal transmission eliminates this advantage, supporting evolutionary theory.

Keywords:

Bacteriophage benevolence cooperation evolution f1 mode of transmission

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Area of Science:

Evolutionary biology
Microbiology
Parasitology

Background:

Cooperation between parasites and hosts is a key area in evolutionary biology.
The mode of parasite transmission (vertical vs. horizontal) is theorized to be critical for maintaining cooperation.
Horizontal transmission involves parasite progeny infecting unrelated hosts, while vertical transmission involves infecting related hosts.

Purpose of the Study:

To test the paradigm that parasite transmission mode dictates the evolution of host-parasite cooperation.
To investigate whether vertical transmission selects for more cooperative parasite strains.

Main Methods:

Utilized bacteria and filamentous bacteriophage (f1) for experimental testing.
Manipulated culture conditions to control parasite transmission modes: vertical-only and allowing horizontal spread.
Monitored selection of parasite variants based on host growth rate and transmission efficiency.

Main Results:

Under vertical transmission conditions, selection favored parasite variants that were most benevolent, minimizing harm to host growth rate.
When horizontal transmission was permitted, the selective advantage of benevolent parasite variants was lost.
Experimental results align with theoretical predictions regarding transmission mode and cooperation.

Conclusions:

The mode of parasite transmission is a significant determinant in the evolution of cooperation between parasites and hosts.
Vertical transmission promotes the evolution of cooperation by favoring less harmful parasite strains.
Horizontal transmission disrupts the selective pressures that maintain cooperation.