Data for: Sexual Selection and the Non-random Union of Gametes: Retesting for Assortative Mating by Fitness in Drosophila melanogaster

While numerous theoretical population genetic models indicate that mating assortatively by genetic ‘quality’ in a species can enhance the efficiency of purging of deleterious mutations and/or the spread of beneficial alleles in the gene pool, empirical studies looking to quantify the extent of assortative mating by quality are surprisingly rare and largely inconclusive. Here, we set out to examine whether fruit flies (Drosophila melanogaster) engage in assortative mating by body-size phenotype, a composite trait strongly associated with both reproductive success and survival, and is considered a reliable indicator of natural genetic quality.

Male and female flies of different body-size sizes classes (large and small) were obtained under the typical culture conditions to which they were adapted and placed into competitive reproductive conditions, so that their interactions and mating patterns could be measured. We found that flies engaged in assortative courting and mating behaviours and that they produced more offspring with similar sized individuals. Subsequent assays of offspring fitness indicated that assortative mating produced sons and daughters that had greater or equal reproductive success than those produced from disassortative mating.