Abstract
Altruistic social interactions generally evolve between genetically related individuals or other replicators, whereas sexual interactions usually occur among unrelated individuals. This tension between social and sexual interactions is resolved by policing mechanisms enforcing cooperation among genetically unrelated entities. For example, most organisms with two haploid genomes are diploid, both genomes encapsulated inside a single nuclear envelope. A fascinating exception to this are Basidiomycete fungi, where the two haploid genomes remain separate. Uniquely, the haploid nuclei of the dikaryon can fertilize subsequent gametes encountered, the presumed benefit of this lifecycle. The implications for the balance of selection within and among individuals are largely unexplored. We modelled the implications of a fitness tradeoff at the level of the haploid nucleus versus the level of the fungal individual. We show that the most important policing mechanism is prohibition of fusion between dikaryons, which can otherwise select for detrimental levels of nuclear mating fitness. An additional policing mechanism revealed by our model is linkage between loci with fitness consequences. Our results show that benefits of di-mon matings must be paired with policing mechanisms to avoid uncontrolled selection at the level of the nuclei. Furthermore, we discuss evolutionary implications of recent claims of nuclear exchange in related fungal groups.
Competing Interest Statement
The authors have declared no competing interest.
