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Cheating does not explain selective differences at high and low relatedness in a social amoeba
Gerda Saxer1, Debra A Brock, David C Queller
1Department of Ecology and Evolutionary Biology MS 170, Rice University, 6100 Main Street, Houston, TX 77005, USA. gsaxer@rice.edu
BMC Evolutionary Biology
|March 16, 2010
Summary
High relatedness in Dictyostelium discoideum favors a single clone, while low relatedness allows multiple clones to persist. Social competition, not cheating, drives these outcomes in the social amoeba.
Area of Science:
- Evolutionary biology
- Behavioral ecology
- Microbiology
Background:
- Altruism in Dictyostelium discoideum is linked to relatedness, with some amoebae sacrificing themselves to form stalks for spore dispersal.
- Genetic diversity during aggregation can lead to conflict over resource allocation (spores vs. stalk).
Purpose of the Study:
- To investigate the effect of relatedness on the population dynamics of genetically distinct Dictyostelium discoideum strains.
- To determine if social cheating or other factors explain strain composition under varying relatedness conditions.
Main Methods:
- Experimental populations of Dictyostelium discoideum were established using eight genetically distinct wild isolates.
- Twelve replicated populations were maintained under high and low relatedness treatments.
- Strain composition was assessed after one and ten social generations.
Main Results:
- A single clone dominated all populations at high relatedness.
- Three clones predominated in all populations at low relatedness.
- Social cheating did not explain the observed population structures; instead, high spore production and short unicellular stage duration were key factors for successful clones at low relatedness.
Conclusions:
- Social competition during the vegetative stage, beyond solitary growth differences, significantly impacts Dictyostelium discoideum population dynamics.
- The high repeatability of results underscores the strength of these interactions and suggests novel research approaches are needed.
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