RT Journal Article
SR Electronic
T1 Selection for altruistic defense in structured populations
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 733899
DO 10.1101/733899
A1 Felix Jordan
A1 Martin Hutzenthaler
A1 Dirk Metzler
YR 2019
UL http://biorxiv.org/content/early/2019/08/14/733899.abstract
AB We model natural selection for or against an altruistic defense allele of a host (or prey) against a parasite (or predator). The populations are structured in demes and we specify rates for birth, death, and migration events of single individuals. The defense behavior has a fitness cost for the actor and locally reduces parasite growth rates. In a previous study (Hutzenthaler et al., 2015), we analytically derived a criterion for fixation or extinction of altruists in the limit of large populations, many demes, weak selection and slow migration. Here, we use two simulation approaches to analyze the model in relaxed settings. We confirm that the criterion still holds for settings with finitely many demes with various migration patterns if populations are large and the ecological interactions are fast compared to evolutionary processes. For smaller populations with no complete separation of evolutionary and ecological time scales, the value of the shift between fixation and extinction changes, but the qualitative insights remain valid. The key mechanism of providing a benefit of altruism is randomness of reproduction and death events leading to differences in population sizes between demes. Randomness, which is more pronounced for small populations, improves the conditions for fixation of the altruistic allele. Furthermore, as suggested by the previous asymptotic results, we find no significant effect of the migration rate and conclude that the amount of gene flow under which the evolution of altruism is favored may not be as limited as suggested by previous studies.