Male Grijalva mosquitofish (Heterophallus milleri Radda, 1987) increase individual mating preferences in front of an audience

Socially influenced mate choice behavior is currently a growing field in the study of sexual selection and evolu- tion. Here, we provide the first description of male Gri- jalva mosquitofish (Heterophallus milleri) courtship behav- ior, and further report on an unparalleled “audience effect” in that species. Lab-reared male Grijalva mosquitofish sig- nificantly increased their preference for an initially pre- ferred female in a full contact design in the presence of another male. This is somewhat unexpected as previous studies found males of other members of the family Poe- ciliidae to interact more evenly with stimulus females when faced with an audience, and thus decreasing their preference for the initially preferred female. As those “audi- ence effects” are assumed to represent male tactics to pre- vent sperm competition risk arising through male mate choice copying, we argue that male mate choice copying might not play a major role in the reproductive biology of H. milleri.