Escape from the Red Queen: an overlooked scenario in coevolutionary studies

Almost all eukaryotic organisms undergo sexual recombination at some stage of their life history. However, strictly asexual organisms should have higher per capita rate of reproduction compared with those that have sex, so the latter must convey some advantage which overrides the reproductive benefit of asexuality. For example, sexual reproduction and recombination may play an important role in allowing organisms to evolutionarily ‘keep up’ with parasites. Host–parasite coevolution can operate via negative frequency‐dependent selection whereby parasite genotypes adapt to infect host genotypes as they become locally common. By producing more genetically diverse offspring with unique genotypes, sexual organisms have an advantage over asexual counterparts. Essentially, sexual hosts are more difficult for coevolving parasites to ‘track’ over time. This scenario has been named the “Red Queen hypothesis”. It refers to a passage in Lewis Carroll's ‘Through the Looking Glass’ in which the Red Queen tells Alice: ‘it takes all the running you can do, to keep in the same place’; this statement resembles the negative frequency‐dependent dynamics of host–parasite coevolution.