Sexually monomorphic wing pigmentation pattern does not contribute to mate choice in Drosophila guttifera

In many animal groups, sexually dimorphic ornaments are thought to be evolved by intraspecific competition or mate choice. Some researchers pointed out that sexually monomorphic ornaments could also be evolved by mate choice by both sexes or either sex. Many species of fruit fly have sexually monomorphic wing pigmentation. However, involvement of their sexually monomorphic ornaments in mate choice has not been tested. We aimed to examine whether the sexually monomorphic polka-dotted pattern on wings of Drosophila guttifera contributes to mate choice. Because D. guttifera does not mate in the dark condition at all and courtship sound was not observed, some visual information is likely to be used in mating behaviour. We compared the number of mates between individuals with and without wings, and found that presence of wings influenced mate choice in both sexes. We then compared the number of mates between individuals bearing replaced wings, one group for conspecific D. guttifera wings and another group for heterospecific D. melanogaster wings with no pigmentation pattern. The effect of conspecific/heterospecific wings was only detected in mate choice by females. By comparison between wild-type and black-painted wings, we found no evidence of contribution of wing pigmentation pattern to mate choice in either sex.