Mate choice copying in the sailfin molly, Poecilia latipinna, in the wild

Mate choice copying has been documented extensively in the laboratory with almost no supporting data available from studies in the wild. We investigated male and female mate choice copying in a wild population of the sailfin molly, a species that shows copying in the laboratory. We set up two upside-down plastic tanks in a river, with two jars of water on each tank. In male mate choice trials we placed a female in one jar and a male in the other on one tank and a female in one jar on the other tank, leaving the last jar empty. In female mate choice trials we presented a male and a female on one tank and a male and an empty jar on the other. Males preferred to associate with a female adjacent to a male rather than a lone female and females preferred to associate with a male adjacent to a female rather than a lone male. In two controls for shoaling behaviour we presented two males on one side of the set-up and one male on the other or two females versus one female. These controls showed that shoaling behaviour could not explain the male and female preference. Thus both sexes of the sailfin molly show mate choice copying in the wild, much as they do in laboratory studies. At least in this species, mate choice copying is not a laboratory artefact.