Flexibility of the Grouping-induced Courtship Behavior in fruM Null Males. (AI) All males were tested either between 2 males of the same genotype (blue), towards D. melanogaster females (red), D. yakuba females (yellow), or D. mojavensis females (cyan). (A–E) Courtship indices of fruLexA/fru4-40 males that had been isolated (A), or grouped with males of the same genotype (B), D. melanogaster females (C), D. yakuba females (D), or D. mojavensis females (E) for 8 days prior to testing. *p < 0.05, **p < 0.01 and ***p < 0.001, one-way ANOVA. (F–I) Courtship indices of wild-type males that had been isolated (F), or grouped with males of the same genotype (G), D. yakuba females (H), or D. mojavensis females (I) for 8 days prior to testing. ***p < 0.001, one-way ANOVA. n = 12~24 for each. Error bars indicate SEM.