Höfundar:
Björn Schäffner
Sex is the dominant mode of reproduction in eukaryotes. Yet, the evolution of sex has baffled evolutionary biologists for decades due to its obvious disadvantages. This reproductive mode comes with staggering costs, predominantly the production of males resulting in only half the reproductive capacity of asexual organisms. Extrinsic factors (such as parasites) were long considered the potential source for promoting sex and recombination. In contrast, asexuals with a greater efficiency producing identical clones through parthenogenesis possess a higher vulnerability towards parasites on a genetic level. The Red Queen Hypothesis postulates that in a coevolutionary arms race evolutionary change is required for survival. Genetic recombination (i.e. mixing of parental genes) is an evolutionary advantage to provide offspring with a temporary escape (fitness increase, resistance) from rapidly evolving parasites, until those, in turn, coevolve and overcome the genetically-coded defense mechanisms to maintain a constant virulence level. A discontinuation of evolutionary change would ultimately lead to extinction especially under strong selection pressures imposed by parasites. Numerous theoretical and experimental investigations with varying biological parameters have shown that parasites predominantly infect genetically uniform host lineages, while genetically diverse, sexually reproducing host populations cope better with their biological enemies. The direct empirical evidence accentuates the contribution of parasites to the continued presence of sexual reproduction and genetic polymorphism as a safeguard against extinction – thank you parasites!
