Rare male mating advantage for inversion karyotype in Drosophila ananassae.

These experiments were conducted to study frequency-dependent sexual selection on the alpha inversion in the left arm of the second chromosome (2L) in Drosophila ananassae. Two different strains, ST/ST-standard gene arrangement and AL/AL-alpha inversion in 2L were used. Female-choice experiments were carried out in five different male ratios. Two different methods of observation have been employed, one in which copulating pairs are aspirated out and the other, in which pairs are not removed. Results were analyzed by chi(2) tests, and log odds plus regression analyses. Regression analyses revealed the presence of one-sided rare male mating advantages for AL/AL males. Preferential mating is present within the strain having AL/AL karyotype. The minority male advantage and preferential mating found in the AL/AL strain are different components of mating success. ANOVA fails to show any significant difference between the outcomes of rare-male experiments using these two different methods.