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Negative Frequency-Dependent Selection Promotes Strain Structure in a Plant Pathogen
Shuanger Li1,2, Eric Laderman1, Hanna Märkle1,3
1Department of Biology, New York University, New York, New York, USA.
Ecology Letters
|January 4, 2026
Summary
Negative frequency-dependent selection (NFDS) drives Pseudomonas syringae strain diversity and modularity. Eco-evolutionary dynamics maintain pathogen coexistence by adapting virulence to dominant hosts.
Area of Science:
- Microbial ecology
- Evolutionary biology
- Genomics
Background:
- Microbial virulence factors and host defense proteins interact, potentially creating negative frequency-dependent selection (NFDS).
- High strain diversity in Pseudomonas syringae has been observed, but the underlying population structure is not fully understood.
- Previous studies noted strain diversity but lacked explanations for observed modular structures.
Purpose of the Study:
- To investigate the role of NFDS in maintaining Pseudomonas syringae strain diversity and structure.
- To explore the relationship between effector repertoires, host interactions, and pathogen evolution.
- To model the eco-evolutionary dynamics shaping pathogen populations.
Main Methods:
- Characterization of 76 Midwestern US and 1104 global Pseudomonas syringae strains.
- Analysis of strain diversity, modular structure, and phylogenetic relationships.
- Development and application of a stochastic computational model for effector repertoires.
Main Results:
- Confirmed high strain diversity in Pseudomonas syringae.
- Revealed that strains are structured into similarity modules, not explained by host, location, or genetic linkage alone.
- Demonstrated that NFDS generates and maintains modular strain structure, even with genetic exchange.
Conclusions:
- NFDS is crucial for generating and maintaining modularity in Pseudomonas syringae populations.
- Modular structure arises from pathogen groups adapted to dominant hosts.
- Eco-evolutionary dynamics facilitate strain coexistence through niche-specific adaptations.
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