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Strong Gene Flow Undermines Local Adaptations in a Host Parasite System
Perttu Seppä1, Mariaelena Bonelli2,3, Simon Dupont3
1Centre of Excellence in Biological Interactions, Organismal and Evolutionary Biology Research Program, Faculty of Biological and Environmental Sciences, University of Helsinki, P.O. Box 65, 00014 Helsinki, Finland.
Insects
|September 5, 2020
Summary
Host-parasite co-evolution is shaped by genetic potential. Despite geographic barriers, gene flow between social wasps Polistes biglumis and Polistes atrimandibularis is not restricted, challenging theories of local adaptation.
Area of Science:
- Evolutionary Biology
- Ecology
- Genetics
Background:
- Co-evolutionary dynamics between hosts and parasites are influenced by adaptive potential and genetic architecture.
- Geographic variation in selection pressures can lead to a geographic mosaic of co-evolution.
- The social wasp Polistes biglumis and its parasite Polistes atrimandibularis provide a model system for studying local adaptation in interacting species.
Purpose of the Study:
- To investigate the spatial genetic structure of Polistes biglumis and Polistes atrimandibularis populations at local and regional scales in the Alps.
- To assess the role of gene flow in shaping co-evolutionary trajectories in this host-parasite system.
- To test the hypothesis that restricted gene flow is necessary for the evolution of local adaptations.
Main Methods:
- Analysis of spatial genetic structure using nuclear markers (DNA microsatellites, AFLP) and mitochondrial sequences.
- Comparison of genetic variation and population differentiation between the host (P. biglumis) and parasite (P. atrimandibularis).
- Inference of net dispersal patterns from genetic differentiation data.
Main Results:
- Both host and parasite populations exhibited similar levels of genetic variation.
- Host populations lacked genetic structure at the local scale, but significant regional differentiation was observed in both species across all markers.
- Net dispersal inferred from genetic differentiation was similar between host and parasite, suggesting that apparent barriers like mountains do not restrict gene flow significantly.
Conclusions:
- Apparent dispersal barriers in the Alps do not significantly restrict gene flow between P. biglumis and P. atrimandibularis.
- There are no substantial differences in gene flow between the host and parasite species.
- These findings contradict the hypothesis that restricted gene flow is a prerequisite for the evolution of local adaptations in host-parasite systems.
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