Anal fin pigmentation in <i>Brachyrhaphis</i> fishes is not used for sexual mimicry

<div><p>Mimicry can occur in several contexts, including sexual interactions. In some cases, males mimic females to gain access to potential mates. In contrast, there are relatively few examples of species where females mimic males, and we know very little about what drives these patterns. Two hypotheses have been advanced to explain female mimicry of males. The first is that mimicry is used to reduce harassment of females by males. The second is that mimicry is used to display dominance over other females. In this study, we tested these hypotheses in <i>Brachyrhaphis</i> fishes, wherein females of several species have pigmentation on their anal fin of the same coloration and shape, and in the same location, as the genitalia of males. To test if female mimicry of males reduces male harassment, we experimentally manipulated female pigmentation and observed male preference for females with and without male-like pigmentation. To test the effect that female mimicry of males has on female dominance, we observed how females respond to anal fin pigmentation patterns of companion females. We found that neither of these hypotheses was supported by our data. We conclude that similarities in anal fin pigmentation between male and female <i>Brachyrhaphis</i> fishes is not an adaptation to reduce male harassment or to signal dominance between females. Alternative explanations must exist, including the possibility that these similarities are simply non-adaptive.</p></div

Results of male dichotomous choice test comparing the amount of time (in seconds) males spent with either pigmented or non-pigmented females.

<p>In all species the difference in the association time between pigmented and non-pigmented females was not statistically significant (P>0.05 in all cases). Error bars represent standard error calculations.</p

Gonopodial and anal fin pigmentation in male (on left) and female (on right).

<p><i>Brachyrhaphis</i> fishes: (A) <i>B</i>. <i>rhabdophora</i>; (B) <i>B</i>. <i>roseni</i>; and (C) <i>B</i>. <i>terrabensis</i>.</p

A comparison of aggression levels between pairs of females with either matching or non-matching levels of anal fin pigmentation evaluated by species.

<p>A comparison of aggression levels between pairs of females with either matching or non-matching levels of anal fin pigmentation evaluated by species.</p