Data from: Sex increases the probability of evolutionary rescue in the presence of a competitor: sex is beneficial in presence of competitors

The explanation for the continued existence of sex, despite its many
costs, remains one of the major challenges of evolutionary biology.
Previous experimental studies have demonstrated that sex increases the
rate of adaptation in novel environments relative to asexual reproduction.
Whilst these studies have investigated the impact of sex on adaptation to
stressful abiotic environments, the potential for biotic interactions to
influence this advantage of sex has been largely ignored. Species rarely
exist in isolation in natural conditions, so the impact of sex on
adaptation to a stressful abiotic environment may be altered by the
interactions between coexisting species. To investigate the interplay of
sex and competition on adaptation to deteriorating conditions, we allowed
populations of the unicellular alga (Chlamydomonas reinhardtii) to evolve
in an environment to which they were initially poorly adapted. We
manipulated both their mode of reproduction and the presence of a
competitor, and monitored population size and proportion of evolutionary
rescue events for each mode of reproduction. The results indicate that sex
may be the beneficial strategy in the presence of the competitor. Sexual
populations had highest probability of evolutionary rescue irrespective of
the presence of the competitor. The overall advantage of sex was also
manifested through higher level of adaptedness of survived sexual
populations relative to asexual populations. Since competitive
interactions are commonplace in nature, one of the explanations for the
maintenance of sex by natural selection may be the increased rate of
adaptation of sexual populations both in the presence and absence of
competitors.