Experimental Studies of the Evolutionary Significance of Sexual Reproduction. I. A Test of the Frequency-Dependent Selection Hypothesis

Abstract

This study tests the hypothesis that one evolutionary advantage of sexual reproduction is that it produces rare or unique genotypes with a frequency-dependent advantage. Our experimental approach involved planting clonal tillers of the grass Anthoxanthum odoratum into natural sites. In two different experiments, clones in situations as a minority genotype had approximately a twofold increase of fitness compared to those in majority genotype situations. Although fitness data were strongly skewed and highly variable, overall these differences were significant. The data reported here are in concordance with the theoretical expectations of the frequency-dependent hypothesis for the evolutionary significance of sex and represent the first experimental demonstration of frequency-dependent selection under natural field conditions.