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.     

花生雌雄两性细胞发育关系的研究

本试验结果表明 ,雌雄配子体形成过程和程序与前人结论相一致 ,但发现 :1 )尽管雌雄蕊同时形成 ,但在雌雄配子形成不同步的情况下 ,花粉和胚囊中的大量淀粉却能同时充实 ,并且同时成熟等待受精。 2 )大孢子母细胞形成比小孢子母细胞迟 0 .7～ 0 .8片展叶 ;雌配子体形成比雄配子体迟 0 .5～ 0 .6片展叶。 3)雌雄两性细胞发育特点不同 ,雄性是小孢子形成快而花粉粒发育慢 ,雌性是大孢子形成慢而胚囊发育快 ,为此在所用时间上 ,花粉粒发育约是小孢子形成的 1 .6倍 ,是胚囊发育的 2 .3倍 ,而大孢子形成约是胚囊发育的 2 .2倍 ,约是小孢子形成的 1 .4倍。     

Male Mating Tactics in Captive Rhesus Macaques (Macaca mulatta): The Influence of Dominance, Markets, and Relationship Quality

Male mating success in a multimale–multifemale group can depend on several variables: body condition, dominance, coalitions, “friendship,” or an exchange of services for mating access. Exchange patterns may also be determined by market effects or social relationships. We studied the mating tactics of males in a captive, multimale–multifemale group of rhesus macaques and the resulting patterns of mating and paternity to determine the influence of dominance rank, mating markets, and relationship quality on their mating tactics. Male rank was positively related to the total number of copulations and the number of mating partners, but did not explain male mating distribution completely. Moreover, male fertilization success was not related to male rank. Males did not exchange grooming for mating access on the same day and neither the supply nor the rank (as a proxy for quality) of receptive females affected the amount of male grooming, suggesting that market effects did not explain male mating access. However, there was a positive correlation between long-term grooming patterns of both males and females and mating access, indicating that social relationships were important for male mating access. Paternity data revealed that these social relationships were also important for male reproductive success. We conclude that both male rank and male–female “friendship” determined male mating access in these rhesus macaques, but that “friendship” was more important in determining paternity, emphasizing the importance of intersex social bonds in male mating success in multimale primate societies.     

The Relative Contributions of Facial Shape and Surface Information to Perceptions of Attractiveness and Dominance

Although many studies have investigated the facial characteristics that influence perceptions of others’ attractiveness and dominance, the majority of these studies have focused on either the effects of shape information or surface information alone. Consequently, the relative contributions of facial shape and surface characteristics to attractiveness and dominance perceptions are unclear. To address this issue, we investigated the relationships between ratings of original versions of faces and ratings of versions in which either surface information had been standardized (i.e., shape-only versions) or shape information had been standardized (i.e., surface-only versions). For attractiveness and dominance judgments of both male and female faces, ratings of shape-only and surface-only versions independently predicted ratings of the original versions of faces. The correlations between ratings of original and shape-only versions and between ratings of original and surface-only versions differed only in two instances. For male attractiveness, ratings of original versions were more strongly related to ratings of surface-only than shape-only versions, suggesting that surface information is particularly important for men’s facial attractiveness. The opposite was true for female physical dominance, suggesting that shape information is particularly important for women’s facial physical dominance. In summary, our results indicate that both facial shape and surface information contribute to judgments of others’ attractiveness and dominance, suggesting that it may be important to consider both sources of information in research on these topics.     

The Function of Male Dominance in the Eusocial Wasp, Mischocyttarus mastigophorus (Hymenoptera: Vespidae)

Males of a Neotropical eusocial wasp, Mischocyttarus mastigophorus , are dominant over their female nest mates. Mischocyttarus mastigophorus males behave aggressively toward females, while females rarely bite or chase males. Aggressive interactions between the sexes are behaviorally indistinguishable from dominance interactions among females. Males are long-lived as adults, and can reside on nests for periods of at least one month. Furthermore, males comprise a large proportion of post-emergence colony populations throughout much of the colony cycle. Males on the nest perform maintenance tasks at low rates, but contribute little other labor to their colonies. Males do not forage, but consume a disproportionate amount of the food (nectar and insect prey) collected by workers. Males in some colonies direct disproportionate amounts of aggression toward their queens, which may further contribute to males' food procurement. These data suggest that adult males represent a considerable energetic and labor cost to their colonies. I hypothesize that the dominance structure of M. mastigophorus directs food resources to adult males, with the function of increasing their longevity. Increased male longevity may be selectively advantageous in tropical species such as M. mastigophorus that found new colonies throughout much or all of the year. When females initiate new nests over much of the year, individual males' mating opportunities may be temporally distributed, favoring longer adult lifespans. Male dominance is predicted to occur in other populations of independent-founding Neotropical Polistinae with asynchronous colony foundation.     

The Relationship Between Resource Control, Association with Females and Male Weapon Size in a Male Dominance Insect

In species with a resource‐defence (male dominance) mating system, males are expected to maximize fitness by controlling resources deemed more valuable by sexually receptive females because these sites attract more mates. Furthermore, males, which control more valuable resources should themselves be of high quality. I experimentally tested these predictions in the laboratory using the sexually dimorphic Wellington tree weta, Hemideina crassidens (Blanchard) (Orthoptera: Tettigonioidea: Anostostomatidae). Male H. crassidens use their mandibular weaponry to fight for control of harems (groups of adult females) that seek shelter in trees cavities (galleries). As predicted, larger galleries housed significantly larger groups of females and males with larger weaponry controlled large galleries significantly more often. Therefore, galleries with a larger volume are likely considered more valuable by males because they house larger harems. However, contrary to prediction, males with larger weaponry did not reside with significantly more females overall because females did not always form the largest possible groups in galleries and males with smaller weaponry were able to reside with single females in small galleries. The latter observation suggests a possible alternative mating strategy by disadvantaged males.     

Gender and Facial Dominance in Gaze Cuing: Emotional Context Matters in the Eyes That We Follow

Gaze following is a socio-cognitive process that provides adaptive information about potential threats and opportunities in the individual’s environment. The aim of the present study was to investigate the potential interaction between emotional context and facial dominance in gaze following. We used the gaze cue task to induce attention to or away from the location of a target stimulus. In the experiment, the gaze cue either belonged to a (dominant looking) male face or a (non-dominant looking) female face. Critically, prior to the task, individuals were primed with pictures of threat or no threat to induce either a dangerous or safe environment. Findings revealed that the primed emotional context critically influenced the gaze cuing effect. While a gaze cue of the dominant male face influenced performance in both the threat and no-threat conditions, the gaze cue of the non-dominant female face only influenced performance in the no-threat condition. This research suggests an implicit, context-dependent follower bias, which carries implications for research on visual attention, social cognition, and leadership.     

Canine Length in Wild Male Baboons: Maturation,Aging and Social Dominance Rank

Canines represent an essential component of the dentition for any heterodont mammal. In primates, like many other mammals, canines are frequently used as weapons. Hence, tooth size and wear may have significant implications for fighting ability, and consequently for social dominance rank, reproductive success, and fitness. We evaluated sources of variance in canine growth and length in a well-studied wild primate population because of the potential importance of canines for male reproductive success in many primates. Specifically, we measured maxillary canine length in 80 wild male baboons (aged 5.04–20.45 years) from the Amboseli ecosystem in southern Kenya, and examined its relationship with maturation, age, and social dominance rank. In our analysis of maturation, we compared food-enhanced baboons (those that fed part time at a refuse pit associated with a tourist lodge) with wild-feeding males, and found that food-enhanced males achieved long canines earlier than wild-feeding males. Among adult males, canine length decreased with age because of tooth wear. We found some evidence that, after controlling for age, longer canines were associated with higher adult dominance rank (accounting for 9% of the variance in rank), but only among relatively high-ranking males. This result supports the idea that social rank, and thus reproductive success and fitness, may depend in part on fighting ability mediated by canine size.     

The Influence of Dominance on Shelter Preference and Eviction Rates in the Crayfish, Orconectes rusticus

The establishment and reinforcement of dominance status is thought to provide an individual with increased access to preferred resources, such as food, mates, and shelter. Resources within an environment vary based on their availability, abundance, and specific characteristics of the resource. Animals can exhibit preferences for resources by increasing the intensity of competition for access to the resource. We investigated the role that dominance has in acquiring and controlling resources within crayfish populations. Populations of 5 size‐matched crayfish were allowed to establish a social hierarchy in the presence of shelters of differing structure in 10 different trials. Crayfish agonistic interactions and the use and control of shelters were quantified from 96 h continuous video recordings. Shelter preference was defined by crayfish use of specific shelter types that were occupied for longer durations. Analysis of the social hierarchy demonstrated that crayfish have a linearity hierarchy in this context. In addition, it is clear that dominance rank had a significant impact on shelter use, shelter acquisition, and shelter eviction. Crayfish with lower average dominance ranks selected specific shelter types (smaller and fewer openings). Dominant crayfish used big shelters and were less likely to be evicted from shelters. These results demonstrate that dominance in crayfish serves a role in the acquisition of resources and is also important for the control of those resources.     

On the Relationship between Aggression and Social Dominance

It is frequently assumed that variation in dominance status is in large part a function of differences in levels of aggressiveness. This assumption and the reasoning underlying it are examined in this paper. It is argued that the large role ascribed to aggression with respect to dominance success results from a conceptual error, in particular, the temptation to conflate the two constructs. There may be an association between aggression and social dominance, not because levels of aggression determine dominance success, but because aggression is a manifestation of dominance. It is further argued that the analysis of dominance relationships exclusively in terms of individual attributes such as aggression is flawed. Social dominance is a relational quality, which could be profitably studied from a sociological perspective.     

Apical Dominance Control in Ipomoea nil: The Influence of the Shoot Apex, Leaves and Stem

The outgrowth of lateral buds is known to be controlled by theupper shoot tissues, which include the apex, the young leavesand the upper stem. An analysis of the influence of these plantparts on axillary bud elongation in Ipomoea nil was carriedout by various treatments on these specific tissues. A restriction of elongation in the main shoot due to eitherdecapitation or shoot inversion resulted in the release of apicaldominance A non-linear type of compensating growth relationshipwas observed between the 13 cm apical growing region of thestem and the lateral buds. It was determined by decapitation,defoliation and AgNO₃ treatments that both the 13 cm stem-growthregion and the young leaves (1–5 cm in length) had a muchgreater inhibitory influence on the outgrowth of specified lateralbuds than did the stem apex (consisting of the terminal 0.5cm of the shoot). The specified lateral buds which were analyzedfor outgrowth were located a number of nodes below the shootapex. The intervening nodes were debudded. Although the importanceof young leaves in the control of apical dominance has beenpreviously recognized, the most significant result from thepresent study with Ipomoea was the strong influence of the 13cm apical growth region of the stem on the out growth of thelateral buds. Apical dominance, Ipomoea nil L., Pharbitis nil, growth region, lateral bud outgrowth, decapitation, defoliation, shoot inversion     

Dominance Modifiers in NEUROSPORA CRASSA: Phenocopy Selection and Influence on Certain Ascus Mutants

When homozygous in zygotes, mutant alleles at the peak locus in linkage group V of Neurospora crassa initiate aberrant asci that are nonlinear, in contrast to the linear asci characteristic of wild type. Most mutant alleles are recessive, inasmuch as crosses of the mutant strains with wild type give linear asci. However, five different mutant alleles, when heterozygous with the wild-type allele, act in varying degrees as zygote dominants, initiating both linear and nonlinear asci, the relative proportions depending on the allele. Five modifiers that act on the dominance relationships of at least one of the five possible heterozygotes of a dominant peak and its wild-type allele have been characterized, four of them having been obtained by selection directed against a phenocopy of these mutants induced by treatment of wild type with l-sorbose. The pattern of modifier specificity observed among the various dominant peak heterozygotes indicates that the phenotypic effects are produced by a complex relationship between the modifiers and the dominant peak alleles in relation to their wild-type allele. In all but two cases the direction of modification, where present, is towards decreasing the dominance of the mutant allele in the heterozygote, evidenced by an increase in the percentage of linear asci when compared with control data. The modifiers exert their maximum modification when they themselves are heterozygous with their wild-type alleles and when the dominant peak allele is heterozygous with its wild-type allele. No modification occurs when heterozygous modifiers are included in zygotes homozygous for a dominant peak allele, reinforcing the notion that the modifiers act on the dominance relationship existent between a dominant peak allele and its wild-type allele, rather than influencing some activity of the mutant allele itself. The modifiers have no detectable effect of their own on ascus morphology, since homozygous modifier zygotes initiate entirely linear asci when only wild-type alleles of peak are present in the zygotes. Their only detectable effect, other than dominance modification, appears to be in conferring sorbose resistance to the mycelium. The modifiers are unlinked to the peak locus, and, except for two of them, they are nonallelic.     

Digit ratio (2D:4D) and the spatial representation of magnitude

Digit ratio (as a putative indicator of prenatal androgen exposure) is related to a range of sexually dimorphic abilities, including spatial skills and mathematical ability. This study examined a phenomenon known as the SNARC effect (Spatial Numerical Association of Response Codes), which is taken as evidence of a mental representation of magnitude along a left-right-oriented number line, with low magnitudes associated with the left side of space, and high numbers with the right side of space. Participants made a parity judgement of numbers with responses made with a left key to odd numbers and a right key to even numbers. This was reversed for a second block of trials. Response times to numbers one to nine with both the right and left hand were calculated, and regression analyses conducted to analyse whether lower magnitudes were responded to faster with the left hand and higher magnitudes with the right hand. Participants with lower (more masculine) digit ratios on the right hand showed a stronger SNARC effect compared to participants with high digit ratios. This pattern of results was also found when the analyses were conducted separately for men and women. Results from left hand digit ratios indicated that only low digit ratio females showed a significant SNARC effect. These findings add to a growing literature on the relationship between digit ratio and cognitive abilities; in this case, simple cognitive representations that are accessed automatically rather than complex skills such as mental rotation or "mathematics" where a variety of solution strategies may be utilised.     

2D:4D Asymmetry and Gender Differences in Academic Performance

Exposure to prenatal androgens affects both future behavior and life choices. However, there is still relatively limited evidence on its effects on academic performance. Moreover, the predicted effect of exposure to prenatal testosterone (T)–which is inversely correlated with the relative length of the second to fourth finger lengths (2D:4D)–would seem to have ambiguous effects on academic achievement since traits like aggressiveness or risk-taking are not uniformly positive for success in school. We provide the first evidence of a non-linear, quadratic, relationship between 2D:4D and academic achievement using samples from Moscow and Manila. We also find that there is a gender differentiated link between various measures of academic achievement and measured digit ratios. These effects are different depending on the field of study, choice of achievement measure, and use of the right hand or left digit ratios. The results seem to be asymmetric between Moscow and Manila where the right (left) hand generates inverted-U (U-shaped) curves in Moscow while the pattern for hands reverses in Manila. Drawing from unusually large and detailed samples of university students in two countries not studied in the digit literature, our work is the first to have a large cross country comparison that includes two groups with very different ethnic compositions.     

Re-examining the Manning hypothesis: androgen receptor polymorphism and the 2D:4D digit ratio

The ‘Manning hypothesis,’ the idea that small differences in the ratio of the lengths of the human second to fourth digits—the 2D:4D ratio—reflect differences in the level of fetal androgen exposure, has been highly influential in the biological and biobehavioral sciences. The ratio is widely used to investigate the involvement of fetal androgens in the differentiation of sexually dimorphic traits. The validity of such studies is based on the premise that individual differences in the size of the 2D:4D ratio mirror differences across individuals in developmental levels of androgen exposure in a dose-dependent manner. Despite its widespread adoption by researchers, clinical evidence has yet to confirm that individual gradation in the ratio denotes differences in testosterone action. Key support for the view that 2D:4D does, in fact, reflect fetal testosterone in a graded fashion is the finding, based on a single small-sample study, that the magnitude of 2D:4D covaries with a polymorphic repeat (CAG) sequence in exon 1 of the gene coding the androgen receptor, AR. In a larger independent sample, we reexamine this genetic association and fail to substantiate a correlation between AR CAG length and 2D:4D. Combined with other recent reports, these data question one of the fundamental pieces of evidence on which the Manning hypothesis rests and raise new issues regarding the extent to which 2D:4D is a valid reflection of differences in fetal testosterone action in normally developing individuals.