Pigmentation patterns can be used as a communication signal in a variety of taxa, and can convey information relative to sexual selection, dominance, and species identification. Pigmentation is also sometimes used in mimicry to deceive the signal receiver into thinking the signaler is something other than itself. Mimicry can occur in several contexts, including sexual interactions, where one sex mimics another. There are relatively few examples of species with females that mimic males. Proposed hypotheses to explain female mimicry of males are that mimicry is used to reduce male harassment or that mimicry is used to display dominance over other females. In this study, we tested these two hypotheses using an experimental approach. Researchers have hypothesized that Brachyrhaphis fishes provide an example of sexual mimicry because females have pigmentation of the same coloration and shape, and in the same location as male genitalia. To test if female mimicry of males reduces male harassment, we designed an experiment to observe 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 female behavior based on the 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 Brachyrhaphis fishes cannot be explained as a way to reduce male harassment of females and is not a good predictor of female dominance interactions. Alternative explanations must exist for this pattern of anal fin coloration include the possibility that these similarities are simply non-adaptive.

In order to maximize fitness, individuals must partition their limited resources among competing physiological processes, creating negative statistical associations between processes known as “life-history trade-offs”. Evidence indicates that individuals tend to decrease their reproductive investment when confronted with a significant immunological challenge in order to increase investment in immune defense. This trade-off is often accompanied by a significant decrease in the sexual signal, which provides an honest signal of the male’s infection status to potential mates. However, if individual residual reproductive value is low, they may instead increase their reproductive investment to maximize reproductive success before the end of their life (a.k.a. terminal investment). Here, we investigate the potential for terminal investment in the ground cricket Allonemobius socius by inoculating males with varying dosages of an immune challenge. We predicted that both high dose and advanced male age would induce terminal investment. Furthermore, we predicted that terminally investing males would produce a dishonest signal by increasing their signaling effort. We found that upon infection We found that upon infection, young males and old males differentially alter their reproductive strategy. Young males exhibited the classic deceleration of reproductive effort. However, old males increased their calling song energetics and decreased their parental investment (nuptial gift size), suggesting that old males are dishonestly signaling their condition to the female.