Differences in female preference for male body size in Poecilia latipinna using simultaneous versus sequential stimulus presentation designs

Female sailfin mollies (Poecilia latipinna) were presented simultaneously with a series of dummy male pairs that differed only in male body size (with dorsal fill size held constant). Females showed a significant directional preference for males of larger body size. However, when presented with the same five dummies in sequence, the same females showed a much weaker preference for increased male body size. To our knowledge, this study is the first of its kind to present to the same females the same set of stimuli in both sequential and paired fashion. Our results showed that females exhibit a much stronger preference for larger males presented simultaneously than when presented in sequence. Female sailfin mollies may therefore more strongly prefer larger males when they can make direct and immediate comparisons between them. These results highlight the importance of considering how females encounter potential mates in nature when designing experiments on female preference in a given species. They also emphasize how the distribution and local density of prospective mates and the context in which they are presented may influence mate choice and sexual selection in general.