# Sexual Selection in Mosquitofish: Differences in the Use of Mating Cues Between Sexes

## TL;DR

The study explores how male and female mosquitofish use different mating cues to choose partners, with females avoiding harassment and males prioritizing reproductive potential.

## Contribution

The study reveals distinct mate choice strategies in G. affinis, emphasizing the role of harassment avoidance in females and multiple cues in males.

## Key findings

- Females prefer males with resting-phase gonopodia to avoid forced copulation.
- Males prefer younger females with larger gravid spots, indicating fecundity.
- Male preference strength correlates with body size and sperm competition intensity.

## Abstract

Mate choice plays a crucial role in evolution, with individuals assessing potential mates based on various traits. The Western mosquitofish (Gambusia affinis), a sexually dimorphic species, provides an ideal model for studying these preferences. This study explored how mating cues influence mate choice in both sexes using morphological data, computer-simulated animations, and preference tests. Results showed that females preferred males with resting-phase gonopodia, likely to avoid forced copulation. Conversely, males preferred younger females, with preference strength increasing with male body size. Additionally, males favored females with larger gravid spots, indicating fecundity, but avoided larger, older females, possibly due to lower reproductive potential. These findings suggest that females prioritize avoiding harassment, while males consider multiple factors in mate selection, highlighting the complexity of mating strategies in G. affinis.

Sexual selection is a major driver of speciation and evolution, with mate choice being a key component. Individuals assess mate quality by integrating various mating cues. The Western mosquitofish (Gambusia affinis), a species exhibiting pronounced sexual dimorphism in body size and secondary sexual traits, serves as an ideal model for studying mate choice. This study examines the impact of mating cues on mate choice in different sexes of G. affinis through a combination of morphological parameter database construction, computer-simulated animations, and dichotomous association preference tests. The results showed that male gonopodium status significantly affects female mate choice. Females exhibited a preference for males with resting-phase gonopodia, suggesting their aversion to forced copulation and sexual harassment in coercive mating systems. Furthermore, males preferred younger females, with this preference being positively correlated with male body size. This suggests that males are sensitive to sperm competition intensity and may base their choice on social rank. Geometric morphometric analysis and simulation experiments showed that males preferred females with larger gravid spots, regardless of age, suggesting that gravid spot size reflects female fecundity. Male preference for younger females with streamlined bodies and smaller abdomens was significant, but body size did not affect mate choice in general. Our findings highlight that female and male G. affinis employ different mate choice strategies, with females prioritizing male harassment avoidance and males considering multiple mating cues, not solely one dominant characteristic, in their mate choice decisions. These findings demonstrate that mate choice in G. affinis involves balancing conflicting preferences for traits associated with reduced harassment risk (e.g., resting-phase gonopodium in males) and those linked to reproductive potential (e.g., large gravid spot in females), highlighting the nuanced decision-making processes in both sexes.