Male coloration affects female gestation period and timing of fertilization in the guppy (Poecilia reticulata)

The trade-up hypothesis is a female behavioral strategy related to mating with multiple males. In this hypothesis, females can produce high-quality offspring while avoiding the risk of losing reproductive opportunities by non-selective mating with males at first mating and then re-mating with more attractive males. As an internal mechanism to realize this behavioral strategy, we predicted that females would immediately fertilize their eggs when they mated with attractive males, whereas females would delay fertilization when they mated with unattractive males to trade-up sires of offspring. The guppy (Poecilia reticulata) is an ovoviviparous fish with internal fertilization, and females show a clear mate preference based on the area of orange coloration on the bodies of males. In addition, it is known that females show a re-mating strategy consistent with the trade-up hypothesis. We tested whether the attractiveness of mated males affected the gestation period and the timing of fertilization. Females were paired with either colorful males or drab males, and the gestation periods (the number of days from mating to parturition) were compared. In addition, we dissected the abdomens of the females at intervals of several days after mating and observed whether the eggs were fertilized. The gestation period in females that were paired with attractive colorful males was significantly shorter than that in females that were paired with drab males. We found that females that mated with colorful males also had their eggs fertilized earlier than those that mated with drab males. Our findings show that differences in the timing of fertilization according to attractiveness of the mate increase the opportunity for cryptic female choice and trading up.

Short-term and long-term mate preference in men and women in an Iranian population

Mate preference in short-term relationships and long-term ones may depend on many physical, psychological, and socio-cultural factors. In this study, 178 students (81 females) in sports and 153 engineering students (64 females) answered the systemizing quotient (SQ) and empathizing quotient (EQ) questionnaires and had their digit ratio measured. They rated their preferred mate on 12 black-line drawing body figures varying in body mass index (BMI) and waist to hip ratio (WHR) for short-term and long-term relationships. Men relative to women preferred lower WHR and BMI for mate selection for both short-term and long-term relationships. BMI and WHR preference in men is independent of each other, but has a negative correlation in women. For men, digit ratio was inversely associated with BMI (p = 0.039, B = − 0.154) preference in a short-term relationship, and EQ was inversely associated with WHR preference in a long-term relationship (p = 0.045, B = − 0.164). Furthermore, men and women in sports, compared to engineering students, preferred higher (p = 0.009, B = 0.201) and lower BMI (p = 0.034, B = − 0.182) for short-term relationships, respectively. Women were more consistent in their preferences for short-term and long-term relationships relative to men. Both biological factors and social/experiential factors contribute to mate preferences in men while in women, mostly social/experiential factors contribute to them.

Differential Effects of Resource Scarcity and Pathogen Prevalence on Heterosexual Women's Facial Masculinity Preferences

The present research focused on how environmental harshness may affect heterosexual women's preferences of potential male mates’ facial characteristics, namely masculinity-femininity. The evidence on this issue is mixed and mostly from Western samples. We aimed to provide causal evidence using a sample of Turkish women and Turkish male faces. A video-based manipulation was developed to heighten environmental harshness perceptions. In the main experiment, participants were primed with either resource scarcity, pathogen prevalence, or neither (control). They then saw masculinized versus feminized versions of the same faces and indicated the face they would prefer for a long-term relationship and separately rated the faces on various dimensions. In general, masculinized faces were perceived as slightly more attractive, slightly healthier, and much more formidable. A multilevel Bayesian model showed that pathogen prevalence lowered the preference for masculinized faces while resource scarcity weakly elevated it. The overall drop of attractiveness ratings in cases of high perceived pathogen prevalence, one of the strongest effects we observed, suggests that during epidemics, formation of new relationships is not a favourable strategy. Implications for evolutionary theories of mate preference are discussed.

Influence of lighting environment on social preferences in sticklebacks from two different photic habitats. II. shoaling and mate preferences of lab-bred fishes

Different environmental conditions may lead to diverse morphological, behavioral and physiological adaptations of different populations of the same species. Lighting conditions, for example, vary vastly especially between aquatic habitats, and have been shown to elicit adaptations. The availability of short-wave ultraviolet (UV) light is especially fluctuating, as UV wavelengths are attenuated strongly depending on water properties. The island of North Uist, Scotland, comprises two differential habitat types, tea-stained and clear-water lakes, varying considerably in UV transmission. In previous studies, wild-caught three-spined stickleback Gasterosteus aculeatus populations (three populations of each habitat type) were tested with respect to their shoaling and mate preferences for fish viewed under UV-present and UV-absent conditions. The results revealed a habitat-dependent preference of UV cues during shoal choice (tea-stained populations: preference for UV-absent condition in tea-stained water; clear-water populations: no preference in clear-water) but an overall preference for UV-present conditions during mate choice. To assess genetic influences on these behavioral patterns, similar experiments were conducted with lab-bred F1-generations of the same stickleback populations that were raised in a common environment (i.e. standardized clear-water conditions). Offspring of sticklebacks from tea-stained lakes tended to prefer shoals viewed under UV-absent conditions (only in tea-stained water), while sticklebacks from clear-water lakes showed a significant preference for the shoal viewed under UV-present conditions in clear-water but not in tea-stained water. Mate-preference experiments demonstrated that females from the tea-stained lakes significantly preferred and females from the clear-water lakes preferred by trend the male viewed under UV-present conditions in the clear-water treatment. The results for both shoaling- and mate-preference tests were largely similar for wild-caught and lab-bred sticklebacks, thus hinting at a genetic basis for the preference patterns.