Experimental studies of the evolutionary significance of sexual reproduction. V. A field test of the sib-competition lottery hypothesis

Abstract

Sexually and asexually derived tillers of Anthoxanthum, odoratum were planted to test the hypothesis that competition among groups of sexual and asexual siblings favors the maintenance of sexual reproduction in populations. Results showed a substantial fitness advantage for sexual tillers, but the advantage of sex did not increase with increasing numbers of colonists in the patch, there were multiple survivors among colonists, and an advantage was observed even for singly planted tillrs. When a truncation-selection scheme was imposed ex post facto on the data, the relative performance of sexual tillers was similar to that predicted by the Bulmer (1980) model, suggesting that sib-competition models fail due to the violation of the assumption of truncation selection. The advantage of sex was not correlated with the presence of other species, total percentage cover, or species diversity, although sites where sex was favored were physically clustered. -from Author