%0 Journal Article
%T Cheating does not explain selective differences at high and low relatedness in a social amoeba
%A Gerda Saxer
%A Debra A Brock
%A David C Queller
%A Joan E Strassmann
%J BMC Evolutionary Biology
%D 2010
%I BioMed Central
%R 10.1186/1471-2148-10-76
%X We found that at high relatedness a single clone prevailed in all twelve populations. At low relatedness three clones predominated in all twelve populations. Interestingly, exploitation of some clones by others in the social stage did not explain the results. When we mixed each winner against the pool of five losers, the winner did not prevail in the spores because all contributed fairly to the stalk and spores. Furthermore, the dominant clone at high-relatedness was not cheated by the other two that persisted at low relatedness. A combination of high spore production and short unicellular stage most successfully explained the three successful clones at low relatedness, but not why one of them fared better at high relatedness. Differences in density did not account for the results, as the clones did not differ in vegetative growth rates nor did they change the growth rates over relevant densities.These results suggest that social competition and something beyond solitary growth differences occurs during the vegetative stage when amoebae eat bacteria and divide by binary fission. The high degree of repeatability of our results indicates that these effects are strong and points to the importance of new approaches to studying interactions in D. discoideum.The evolution of altruism is difficult to explain because altruistic acts benefit other individuals while reducing the fitness of the actor. According to Hamilton's rule, cooperative and altruistic interactions are favored by genetic similarity (with sufficient benefits relative to costs) [1]. This is consistent with high levels of relatedness observed in cooperative organisms, such as social insects [2,3] and spores in a fruiting body of the social amoeba Dictyostelium discoideum [4,5]. Hamilton proposed that genetic similarity among interactors can be increased if individuals can recognize genetically similar individuals or, more passively, if limited dispersal increases the likelihood that neighbors are genetically
%U http://www.biomedcentral.com/1471-2148/10/76