Desired family size and sex of children in Nigeria

During 1981, sex ratio data and preferences for family size and for combinations and permutations of children were provided by 333 Nigerian students at the University of Ilorin, Ilorin, Nigeria. For the present and parental generations combined, the secondary sex ratio was estimated to be 95.8 males:100 females. In the projected families, preferences for family sizes resulted in an average of 4.88 children per family. The most preferred family consisted of four children--a 2m2f combination in a mfmf order, whereas the second most preferred family consisted of five children--3m2f combination in a mfmfm order. Also expressed was a strong preference for permutations of sexes, resulting in a male child as first-born followed by an alternation of sexes. A greater preference for male children was indicated by the combined sex ratio of 167 males:100 females for the preferred families.     

Female mate preferences for male body size and shape promote sexual isolation in threespine sticklebacks

Female mate preferences for ecologically relevant traits may enhance natural selection, leading to rapid divergence. They may also forge a link between mate choice within species and sexual isolation between species. Here, we examine female mate preference for two ecologically important traits: body size and body shape. We measured female preferences within and between species of benthic, limnetic, and anadromous threespine sticklebacks (Gasterosteus aculeatus species complex). We found that mate preferences differed between species and between contexts (i.e., within vs. between species). Within species, anadromous females preferred males that were deep bodied for their size, benthic females preferred larger males (as measured by centroid size), and limnetic females preferred males that were more limnetic shaped. In heterospecific mating trials between benthics and limnetics, limnetic females continued to prefer males that were more limnetic like in shape when presented with benthic males. Benthic females showed no preferences for size when presented with limnetic males. These results show that females use ecologically relevant traits to select mates in all three species and that female preference has diverged between species. These results suggest that sexual selection may act in concert with natural selection on stickleback size and shape. Further, our results suggest that female preferences may track adaptation to local environments and contribute to sexual isolation between benthic and limnetic sticklebacks.     

Variation between and within the sexes in body size preferences

Although it is often assumed that males and females have mating preferences for larger individuals of the other sex, potential underlying differences between male and female preferences for body size are not commonly investigated. Here, sexual differences in body size preferences are examined in the poeciliid fish, Brachyrhaphis rhabdophora. Females preferred larger males to smaller males, but preference did not appear to be affected by female size. One population-level analysis for males did not indicate an overall preference for larger females. A closer examination, however, revealed an effect of male size on preference; larger males preferred larger females, while smaller males preferred smaller females. It appears then that females, regardless of size, share a preference for large males, but males differ in their behaviour, depending on their body size. In addition, while the degree of difference in size between paired females did not appear to affect male preference, the degree of difference in size between paired males strongly affected female preference; the greater the difference, the more strongly females preferred the larger male. Thus, intersexual selection is found to operate in both sexes, but how it operates appears to differ. Intrasexual and intersexual differences in mating behaviour may be missed when evaluating population-wide preferences. That is, there can be underlying differences in how the sexes respond and the consequences of such differences should be considered when investigating mate choice. The results are considered in terms of the evolution of mating preferences, alternative mating strategies, assortative mating, the maintenance of trait variation in a population, and current methods to evaluate mating preferences.     

Fin-mutant female zebrafish (Danio rerio) exhibit differences in association preferences for male fin length

Females often choose to associate with males that have exaggerated traits. In fishes, this may reflect an overall preference for larger size in a potential mate. Female zebrafish (Danio rerio) prefer males with larger bodies but not longer fins. The availability of mutant and transgenic strains of zebrafish make this a unique model system in which to study the role of phenotypic variation in social and sexual behavior. We used mutant strains of zebrafish with truncated (short fin) and exaggerated (long fin) fins to further examine female preferences for fin length in dichotomous association tests. Wild type females showed no preferences between wild type males and short fin mutant males or between wild type males and long fin mutant males. short fin females also showed no preference for short fin males or wild type males while long fin females preferred to associate with long fin males over wild type males. These results suggest that the single gene long fin mutation that results in altered fin morphological may also be involved in a related female association preference.     

Desired family size and sex of children in Libya

During 1982, 600 Arabian students (300 females, 300 males) at the University of Garyounis (Benghazi, Libya) were surveyed to determine their preferences for family size and for combination and permutation of sexes of children. For families of the projected generation, the average number of children was 4.4, the sex ratio was 143.5 males: 100 females, the most preferred combination of sexes was 2m2f, and the most preferred permutation of sexes was mfmf. Strong preferences were indicated for the first-born to be male followed by an alternation of sexes.     

Female preference for trait symmetry in addition to trait size in swordtail fish

Interest in fluctuating asymmetries, random deviations from perfect bilateral symmetry, has spread to studies of sexual selection because of the intriguing idea that females could use the degree of asymmetry of a male trait to assess the genetic quality of potential mates. The evidence that females prefer males with symmetrical sexual signals, however, remains controversial. A problem that applies to most previous studies is that preference for trait size can be misinterpreted as preference for symmetry, even when overall trait size is held constant, if females assess trait size by the largest minimum on one side. If overall trait size is equal between males, the asymmetrical males will have the maximum and minimum trait size, and so preference to mate with symmetrical males could actually reflect a preference to avoid males with the minimum trait on one side. Xiphophorus cortezi females preferred males with symmetrical bar numbers when the minimum number of bars was held constant. The strength of female preference for the symmetrical males was negatively correlated with the strength of preference the same females had for bar number. These results clearly demonstrate that females preferred trait symmetry in addition to trait size.     

MATE CHOICE IN THE SAILFIN MOLLY,POECILIA LATIPINNA

We examined both female and male mate choice in the sailfín molly, Poecilia latipinna. Female mollies preferred larger males over smaller ones when comparing males from their own populations. Although the expression of this preference depends on a female's receptive state, the level of female preference does not appear to be associated with any other attribute of the female or of the males. When presented with males of the same size from different populations, females preferred native over foreign males in some but not all population combinations. These results cannot be explained by a bias for higher size-specific rates of courtship displays that is shared by all females. Males preferred larger over smaller females; larger males exhibited stronger preferences, and preference for the larger female also increased as the disparity in size between the two object females increased. We found no evidence that males preferred native over foreign females when encountered singly or in size-matched combinations. These results indicate that discrimination among populations arises because females exercise divergent directional preferences for size-specific trait values that are associated with differences among males in these values. This result implies an active role for sexual selection in contributing to the maintenance of the behavioral or morphological distinctions among males observed within and among populations.     

Sex steroids modulate changes in social and sexual preference during juvenile development in zebra finches

Zebra finches, like many other animals, have close social relationships mainly with the family at young ages but begin to express interest in opposite-sex extra-family animals as they enter the late juvenile period and sexual maturity. This experiment tested a set of hypotheses that sex steroids are involved in this developmental transition. At 25-30 days, subjects were implanted subcutaneously with Silastic tubes that were empty (controls), filled with testosterone propionate, filled with estradiol benzoate, or filled with a combination of ATD (an aromatization inhibitor) and flutamide (an anti-androgen). Once a week between ages 30 and 90 days, they were given three-choice tests where the three stimulus types were the family members, unpaired males, or unpaired females. The preferred category was defined as the one adjacent to the proximity zone in which the subject spent the most time. Control males were more likely to prefer females and less likely to prefer the family as they got older, and control females were increasingly likely to prefer males. Males treated with testosterone or estradiol showed a premature increase in preferences for females. Females treated with ATD plus flutamide failed to show the normal increase in preferences for males shown by controls. These results indicate an involvement of sex steroids in the maturation of sexual preferences in a socially monogamous species that relies on visual and auditory, rather than olfactory, cues for sexual or other social behavior.     

Male house mice produce fewer offspring with lower viability and poorer performance when mated with females they do not prefer

We report experimental results consistent with the hypothesis that constraints on the expression of male mating preferences affect breeder fitness, offspring viability and performance. If constraints on the expression of mating preferences are common, tests of fitness variation associated with mate preferences must eliminate as many constraints on mate preferences as possible. We tested whether male mate preferences influenced breeder fitness, offspring performance and viability in typically polygynous house mice, Mus domesticus, from a feral source population. Our ‘free mate choice’ trials not only eliminated female preferences, male-male and female-female competition, but also our best guesses of the traits mediating choosers' preferences. Males mated with their preferred (P) females sired more litters than males mated with their nonpreferred (NP) females. Offspring viability was significantly lower when males' reproduced with females they did not prefer compared with females they did prefer. Adult sons of males that mated with their P females were socially dominant to sons of males that mated with their NP females. Adult offspring from P pairings built better nests than offspring from NP pairings. The slope of the survivorship curve for P offspring was significantly higher than for NP offspring. These results showed (1) males' mate preferences affected their fitness, (2) males that mated with females they preferred produced more litters than males that mated with females they did not prefer, and (3) their offspring were significantly more viable and performed significantly better on standardized performance tests. This is the first demonstration of fitness benefits of male choice behaviour in a mammal species with typical paternal investment. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.      

Time course of androgenic modulation of odor preferences and odor cues in male meadow voles, Microtus pennsylvanicus.

During the breeding season, male meadow voles prefer female over male odors and females prefer male over female odors. Testosterone control of males' odor preferences and production of odors attractive to females differ. A male meadow vole's preference for female versus male odor was still evident 1 week after castration, but not 1 week later. This preference was reinstated in testosterone-treated male voles 2 weeks after the onset of hormone replacement. The attractiveness of male odors to females did not disappear until 3 weeks after castration. The attractiveness of male odors was reinstated 1 week after castrated males were treated with testosterone. The time course for the androgenic modulation of production of odors attractive to females may facilitate breeding. For example, at the end of the breeding season males may emit an odor that is still attractive to females. Similarly, at the beginning of the breeding season males may emit an odor that is attractive to females.     

Positive genetic correlation between female preference and offspring fitness

In many species, females display preferences for extreme male signal traits, but it has not been determined if such preferences evolve as a consequence of females gaining genetic benefits from exercising choice. If females prefer extreme male traits because they indicate male genetic quality that will enhance the fitness of offspring, a genetic correlation will evolve between female preference genes and genes that confer offspring fitness. We show that females of Drosophila serrata prefer extreme male cuticular hydrocarbon (CHC) blends, and that this preference affects offspring fitness. Female preference is positively genetically correlated with offspring fitness, indicating that females have gained genetic benefits from their choice of males. Despite male CHCs experiencing strong sexual selection, the genes underlying attractive CHCs also conferred lower offspring fitness, suggesting a balance between sexual selection and natural selection may have been reached in this population.     

Experience Plays a Role in Female Preference for Symmetry in the Swordtail Fish Xiphophorus malinche

Variation in female mating preferences was previously detected in wild-caught Xiphophorus cortezi and Xiphophorus malinche females: smaller (presumed younger) females preferred symmetrical males, while larger (presumed older) females preferred asymmetrical males. We examined the influence of experience on this variation in female preference by determining if X. malinche females would express a preference for symmetry as virgins, shift their preferences for bar symmetry as they got larger (older) and if experience with males of different bar number symmetry could explain the variation in female preference previously detected. Virgin females exhibited no preference for vertical bar number symmetry when tested in the young- or old-age classes. However, young virgins spent more time with the opposite treatment in the second when compared with first test, indicating an ability to detect the difference between symmetry and asymmetry, and potentially a preference to mate with multiple males. When females were reared in one of three treatments, housed with symmetrical, barless or both symmetrical and asymmetrical males, we detected both a treatment and tank effect on strength of preference for symmetry, suggesting that barring pattern and some other aspect of the social environment influenced the development of this mating preference. Finally, we detected no effect of age class on mean strength of preference for symmetry; however, there was a statistically different relationship between female size and strength of preference for symmetry across the two age classes, suggesting that the preference function for symmetry may not be linear in relation to female size.     

GENETIC CORRELATION BETWEEN A FEMALE MATING PREFERENCE AND THE PREFERRED MALE CHARACTER IN SEAWEED FLIES (COELOPA FRIGIDA)

The mating preferences of female seaweed flies Coelopa frigida were determined by observing their acceptance or rejection of males of known size. The inversion karyotype of both males and females was also determined. Females exhibited a preference to mate with large males, and evidence is presented that a genetic correlation exists between the female preference and the preferred trait. Females carrying the inversion karyotype associated with large male size showed a strong preference for large males; females carrying the inversion associated with small male size also exhibited a preference for large males, but it was significantly less strong. This finding suggests that a Fisherian process may be operating.     

Cross-Fostering of Male Mice Subtly Affects Female Olfactory Preferences

The maternal environment has been shown to influence female olfactory preferences through early chemosensory experience. However, little is known about the influence of the maternal environment on chemosignals. In this study, we used two inbred mouse strains, C57BL/6 (C57) and BALB/c (BALB), and explored whether adoption could alter male chemosignals and thus influence female olfactory preferences. In Experiment 1, C57 pups were placed with BALB dams. Adult BALB females then served as the subjects in binary choice tests between paired male urine odours (BALB vs. C57, BALB vs. adopted C57 and C57 vs. adopted C57). In Experiment 2, BALB pups were placed with C57 dams, and C57 females served as the subjects in binary choice tests between paired male urine odours (C57 vs. BALB, C57 vs. adopted BALB, and BALB vs. adopted BALB). In both experiments, we found that females preferred the urine of males from different genetic backgrounds, suggesting that female olfactory preferences may be driven by genetic compatibility. Cross-fostering had subtle effects on female olfactory preferences. Although the females showed no preference between the urine odours of adopted and non-adopted males of the other strain, the BALB females preferred the urine odour of BALB males to that of adopted C57 males, whereas the C57 females showed no preference between the urine odour of C57 and adopted BALB males. Using gas chromatography-mass spectrometry (GC-MS) and stepwise discriminant analysis, we found that the ratios of volatile chemicals from urine and preputial gland secretions were altered in the fostered male mice; these changes may have resulted in the behavioural changes observed in the females. Overall, the results suggest that female mice prefer urine odours from males with different genetic backgrounds; this preference may be driven by genetic compatibility. The early maternal environment influences the chemosignals of males and thus may influence the olfactory preferences of females. Our study provides additional evidence in support of genotype-dependent maternal influences on phenotypic variability in adulthood.     

Female Size Influences Mate Preferences of Male Guppies

Guppies (Poecilia reticulata) have a promiscuous mating system in which female choice for brightly coloured males plays an important role. Consequently, much research on guppies has examined how mate choice by females has lead to the evolution of male colour patterns. Much less attention has been devoted to mate choice by males in this species. In this study, we show that male guppies are choosy when selecting a female to associate with, significantly preferring the larger female when presented with two females that differed by ≥2 mm in standard length (SL). The strength of their preference for each female increased with absolute female size. The relative sizes of the females, however, also influenced male mating preferences: males showed stronger preferences for the larger female as the difference in SL between the two females increased. Such a preference for larger females is not unexpected as fecundity generally increases with body size in female fish. Thus, males choosing to mate with the larger female should have higher reproductive success. An apparent, but non‐significant anomaly, whereby males appear to prefer the smaller of the two females when the difference between female SL was <4 mm, deserves further investigation.     

Female Preference for Male Lateral Projection Area in the Shortfin Molly, Poecilia mexicana: Evidence for a Pre-existing Bias in Sexual Selection

Sailfin molly (Poecilia latipinna) males possess a large dorsal fin (sailfin) and perform an elaborate courtship display. Females prefer to associate and mate with males of greater body and sailfin size. Evidence supports a single origin for the sailfin species complex from a shortfin ancestor. Unlike sailfin species, males of the shortfin species complex are sexually monomorphic in fin size and exhibit little or no courtship behavior. In this study, we tested the pre‐existing bias and lateral projection area (LPA) hypotheses for sexual selection by examining female mating preferences in the shortfin molly, P. mexicana. Specifically, we presented females with pairs of dummy males differing in: (1) dorsal fin and body size together (holding fin:body size ratio constant); (2) body size (holding dorsal fin size constant); (3) dorsal fin size (holding body size constant); and dorsal fin:body size ratio (holding total LPA constant). Females spent more time near dummies of greater body and dorsal fin size. The preference functions based on the first three sets of stimuli showed a similar pattern: the greater the LPA difference between paired dummies, the stronger the preference for the larger of the two. However, in the fourth experiment, neither fin size, body size, nor any particular dorsal fin + body size combination was preferred. These findings support the LPA hypothesis suggesting that increased LPA is more stimulating to sexually receptive females and that females consequently prefer larger males. Moreover, these data are consistent with results obtained in an identical series of experiments conducted on P. latipinna. The preference for increased male dorsal fin size/LPA by both female P. latipinna and P. mexicana supports the pre‐existing bias hypothesis. Thus, a bias for increased male LPA and consequent selection for enlarged dorsal fins may have preceded the appearance of the sailfin trait within the Molliensia lineage.     

Nonvisual mate choice in the Pyrenean mountain newt (<Emphasis Type="Italic">Euproctus asper</Emphasis>): females prefer small males

In many species, females prefer large males as mates. In this paper, we examined whether female Pyrenean mountain newts (Euproctus asper) would show a preference for large males in a simultaneous choice situation. When we tested for a visual preference relative to male body size using visual cues, females did not prefer large males. When chemical cues were presented, females did show a preference, but contrary to our prediction, they preferred the smaller of two males. E. asper males exhibit coercive mating behavior (amplexus), keeping females from feeding for several hours or even days, which may explain why females avoid large, physically stronger, and thus, more coercive males. The predominantly nocturnal lifestyle may explain why visual cues are less important for mate discrimination in this species.     

Female Preferences Based on Male Quality in House Mice: Interaction between Male Dominance Rank and t-Complex Genotype

Considerable evidence indicates that female house mice (Mus domesticus) prefer dominant over subordinate males as mates. In addition, male genotype at the t-complex seems to be an important characteristic used by females in mate choice. Specifically, female mice that carry a t-haplotype at the t-complex prefer +/+ over +/t males as mates. The purpose of the present study was to examine the relative contributions of male dominance rank and male t-complex genotype to female mating preference when both factors were systematically varied. We tested females of three genotypes (+/+, +/t, and t/t) in a preference apparatus using pairs of stimulus males varying in relative dominance status and t-complex genotype. In general, when given the choice, females preferred dominant over subordinate males regardless of the male's t-complex genotype. The preference for dominant males was manifested when both stimulus males were of the same t-complex genotype but differed in dominance rank. In addition, when forced to choose between a dominant +/+ and subordinate +/t or between a dominant +/t and subordinate +/+, females continued to prefer the dominant male. Preference for dominant males was independent of female genotype. Only when both males were dominant but differed in t-complex genotype (i.e. one male was +/+ and the other +/t) or when males were unranked (i.e. had not been used in aggressive encounters to determine dominance rank) did females carrying t-haplotypes manifest preferences for +/+ males. Quite unexpectedly, when both males were subordinate but differed in t-complex genotype, preferences of all females shifted in the direction of the +/t male. It is not clear from present data whether the propensity of females to give greater weight to male dominance rank than to t-complex genotype in choosing mates results in greater fitness. However, if these trends are found in natural populations, it would indicate that the role of mating preference in regulating the frequency of t-haplotypes in wild populations is less straightforward than had been previously thought.     

Prey preferences ofPortia fimbriata,an araneophagic,web-building jumping spider (Araneae: Salticidae) from Queensland

Portia fimbriata from Queensland, a previously studied jumping spider (Salticidae), routinely includes web-building spiders and cursorial salticids in its diet, both of these types of prey being dangerous and unusual prey for a salticid. The present paper is the first detailed study ofP. fimbriata's prey preferences. Three basic types of tests of prey preference were used, providing evidence that (1)P. fimbriata males and females prefer spiders (both web-building spiders in webs and salticids away from webs) to insects; (2)P. fimbriata males and females prefer salticids to web-building spiders; (3)P. fimbriata males and females prefer larger spiders to smaller spiders; (4) there are intersexual differences in the preferences ofP. fimbriata for prey size, females preferring larger prey and males preferring smaller prey; and (5)P. fimbriata's prey preferences are not affected by a prior period without food of 2 weeks. When preferences were tested for by using both living, active prey and dead, motionless lures, the same preferences were expressed, indicating thatP. fimbriata can distinguish among different types of prey independent of the different movement patterns of different prey.     

Independent Mating Preferences for Male Body Size and Coloration in Female Trinidadian Guppies

Although females in numerous species generally prefer males with larger, brighter and more elaborate sexual traits, there is nonetheless considerable intra‐ and interpopulation variation in mating preferences amongst females that requires explanation. Such variation exists in the Trinidadian guppy, Poecilia reticulata, an important model organism for the study of sexual selection and mate choice. While female guppies tend to prefer more ornamented males as mates, particularly those with greater amounts of orange coloration, there remains variation both in male traits and female mating preferences within and between populations. Male body size is another trait that is sexually selected through female mate choice in some species, but has not been examined as extensively as body coloration in the guppy despite known intra‐ and interpopulation variation in this trait among adult males and its importance for survivorship in this species. In this study, we used a dichotomous‐choice test to quantify the mating preferences of female guppies, originating from a low‐predation population in Trinidad, for two male traits, body length and area of the body covered with orange and black pigmentation, independently of each other. We expected strong female mating preferences for both male body length and coloration in this population, given relaxation from predation and presumably relatively low cost of choice. Females indeed exhibited a strong preference for larger males as expected, but surprisingly a weaker (but nonetheless significant) preference for orange and black coloration. Interestingly, larger females demonstrated stronger preferences for larger males than did smaller females, which could potentially lead to size‐assortative mating in nature.