Mean fitness of long-term sexual and asexual populations of Chlamydomonas in benign environments

Populations of Chlamydomonas were maintained in a benign laboratory environment as obligatory sexual or asexual populations for five years. Sexual reproduction is expected to facilitate the elimination of mildly deleterious mutations and thereby increase the mean fitness of a sexual population relative to an asexual population (Kondrashov 1988). Fitness in competition and in pure culture was measured. In neither of the fitness assays, both in solid and liquid cultures of Chlamydomonas, was a fitness advantage of sexual reproduction seen, even though the results varied depending on the definition of fitness. I hypothesized that the effect of mutation clearance could be masked by different forces acting on the selection strain (such as an antagonistic relationship between sexual and vegetative fitness)