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PubMed1988

The influence of a male's dominance status on female choice in Syrian hamsters.

This study evaluated the importance of dominance status on mate selection in Syrian hamsters. In one experiment, sexually receptive females were allowed to choose between tethered males which differed in status. The choice was consistently in favor of the dominant male. The female spent more time in lordosis in the presence of the dominant male. The dominant also obtained a significantly greater number of intromissions. A second experiment investigated whether prior familiarization was essential to permit a female to express mating preferences in a situation where she was free to interact with three males. Again, the dominants were most often preferred and obtained greater sexual access to the female. Prior familiarization or extensive contact with the males was not necessary to support the female's selection of the dominant as a mating partner. The choice occurred quickly, generally within 5 min after contacting the males. Although females did mate with the subordinates, this typically occurred late in the tests. The significance of these data with respect to mate choice and probable paternity effects are discussed.

Animals↗
PubMed1994

Spermatophore size as determinant of paternity in an arctiid moth (Utetheisa ornatrix).

Female Utetheisa ornatrix exercise postcopulatory mate selection, favoring sperm of larger males. Larger males also produce larger spermatophores, raising the question whether males are selected on the basis of body size or the size of their spermatophore. We here present evidence, based on matings in which males were induced to deliver spermatophores disproportionate in size to body mass, that the determinant is spermatophore mass.

Animals↗
PubMed1981

A general analysis of genetic models with frequency-dependent mating. II. Sexual selection for heterozygotes.

Heterozygotes are assumed to mate with a frequency that is any general function, f(v), of their population frequency, v. Models are analysed in which the selection that determines the function f(v) acts either on one sex alone or on both sexes equally. The central equilibrium point v* = 1/2 always exists; it is stable if f(1/2) greater than 1/2. If the central equilibrium is unstable, other asymmetric equilibria may be stable; the fixation states may also be stable. This general analysis is applied to a number of specific models of sexual selection. The models give qualitatively different results. The outcome of selection in population cage experiments could be used to test the alternative models.

Animals↗
PubMed2005

Genetic covariance between indices of body condition and immunocompetence in a passerine bird.

BACKGROUND: Condition-dependence is a ubiquitous feature of animal life histories and has important implications for both natural and sexual selection. Mate choice, for instance, is typically based on condition-dependent signals. Theory predicts that one reason why condition-dependent signals may be special is that they allow females to scan for genes that confer high parasite resistance. Such explanations require a genetic link between immunocompetence and body condition, but existing evidence is limited to phenotypic associations. It remains unknown, therefore, whether females selecting males with good body condition simply obtain a healthy mate, or if they acquire genes for their offspring that confer high immunocompetence. RESULTS: Here we use a cross-foster experimental design to partition the phenotypic covariance in indices of body condition and immunocompetence into genetic, maternal and environmental effects in a passerine bird, the zebra finch Taeniopygia guttata. We show that there is significant positive additive genetic covariance between an index of body condition and an index of cell-mediated immune response. In this case, genetic variance in the index of immune response explained 56% of the additive genetic variance in the index of body condition. CONCLUSION: Our results suggest that, in the context of sexual selection, females that assess males on the basis of condition-dependent signals may gain genes that confer high immunocompetence for their offspring. More generally, a genetic correlation between indices of body condition and imuunocompetence supports the hypothesis that parasite resistance may be an important target of natural selection. Additional work is now required to test whether genetic covariance exists among other aspects of both condition and immunocompetence.

Animals↗
PubMed1997

HLA and mate choice in humans.

Evidence from studies in rodents suggests that mate selection is influenced by major-histocompatibility-complex haplotypes, with preferences for dissimilar partners. This study was initiated to determine whether avoidance of a mate with the same HLA haplotype as one's own might be occurring in the Hutterites, a North American reproductive isolate of European ancestry, notable for their large sibships, communal lifestyle, and limited number of five-locus HLA haplotypes (HLA-A, -B, -C, -DR, and -DQ). HLA haplotypes were known for 411 Hutterite couples. The number of couples expected to match for a haplotype was calculated in two ways: first, from population genotype frequencies, with account being taken of the nonrandom mating pattern with respect to colony lineages, and, second, from computer simulations using conservative founder assumptions and the exact genealogy of the 411 couples. We observed fewer matches for HLA haplotypes between spouses than expected (first method, P = .005; second method, P = .020-.067). Among couples who did match for a haplotype, the matched haplotype was inherited from the mother in 29 cases and from the father in 50 cases (P = .018). These results are consistent with the conclusion that Hutterite mate choice is influenced by HLA haplotypes, with an avoidance of spouses with haplotypes that are the same as one's own.

Adult↗
PubMedDate not supplied

[The hypothesis of immune testing of partners--coordinated adaptations and changes in mating preferences].

Reproductive isolation plays the key role in speciation. According to the prevailing ideas, the main speciation mechanism is gradual accumulation of genetic differences in isolated populations (allopatric phase of speciation) based on mutations, selection, and genetic drift. In this case, reproductive isolation emerges as an occasional byproduct of adaptation to different conditions (ecological speciation) or accumulation of random changes in the gene pool resulting from long-term isolation. Pure sympatric speciation assumes isolation as a direct product of selection (divergent or disruptive selection) that favors individuals selectively mating with their likes. A third possibility is substantiated below. We believe that isolation can be a regular and determined product rather than occasional byproduct of divergence. It can rely on the friend/foe discrimination mechanisms, some of which can be "immune-based" and compare the partner's and own properties (signaling molecules, pheromones, and other antigens in a broad sense). Antigens of the major histocompatibility complex (MHC) can play a substantial role in such testing of potential mates.

Adaptation, Psychological↗
PubMed1996

Reproduction in free-ranging Propithecus verreauxi: estrus and the relationship between multiple partner matings and fertilization.

Female sifaka mate selectively with one or more resident and/or non-resident males during the breeding season. Various adaptive explanations have been advanced to explain why female primates mate with multiple males including that 1) females seek to confuse paternity and thereby forestall male infanticide and/or ensure male infant care or 2) females seek to ensure fertilization. Assessing the power of fertilization insurance to explain mating patterns in females requires information on the temporal relationship between mating and ovarian hormones. The hormonal correlates of reproduction and mating in free-ranging Propithecus verreauxi were investigated using excreted steroids as indices of reproductive state. Solid-phase extraction and radioimmunoassay techniques were used to measure unconjugated estradiol (E(2)) and progesterone (P(4)) in 485 desiccated fecal samples collected from five female sifaka before and during the breeding season at Beza Mahafaly, Madagascar. Results suggest that behavioral estrus was characterized by 10 to 15-day elevations in E(2); hormonal activity was observed to be similar to pseudo-estrus reported for other lemur species; apparent conception was associated with sustained P4 elevations beginning 1 to 3 days post-estrus with gestational phase elevations of E2 beginning 42 to 45 days post-conception; and mating with multiple partners appeared not to be a prerequisite to fertilization, as conception resulted from both monoandrous and polyandrous matings. These preliminary data suggest that fertilization insurance is not adequate to explain polyandrous mating in sifaka at Beza Mahafaly.

Animals↗
PubMed1994

The role of plasma growth hormone, prolactin, triiodothyronine and tetraiodothyronine in the regulation of growth and sex differences in body weight of turkeys.

An attempt was made to alter male:female (M:F) body weight ratios in two strains (S12 and S72) of turkeys by selective matings; to study their post-hatching growth patterns and to relate growth patterns to plasma growth hormone (GH), prolactin (Prl), tetraiodothyronine (T4), and triiodothyronine (T3) concentrations. Selection for high and low M:F body weight ratio (HR and LR) was essentially ineffective in both strains. Sex differences in body weight were first significant in S12 at day of age and in S72 at 6 wk. Plasma GH and Prl rose during the first 2 wk of age and fell thereafter while T3 levels decreased and T4 levels increased over time. Differences in plasma hormones between lines and sexes within strains were noted, but showed no consistent patterns. Correlations between GH and growth were mostly negative. When significant, regressions between body weight and GH or gain and GH were generally negative. Significant correlations between Prl and body weight in males were negative whereas they were of mixed sign in females. Correlations between T3 levels from 2 to 8 wk of age and body weight over this same period were mostly positive in males whereas those at later ages and in females were mostly negative. Few significant correlations between T4 and weight were found. These findings suggest that the regulation of growth in turkeys is quite different than that of mammals and that hormones known to regulate growth in some species may not do so in others.

Age Factors↗
PubMed1977

A model of assortative mating with partial dominance.

A model of assortative mating incorporating partial dominance is proposed for a single locus with two alleles. It is derived by starting from an arbitrary genotypic distribution and finding symmetric and non-selective mating frequencies which duplicate this distribution. Numerical values are imputed to genotypes, the homozygotes having numerically equal values, opposite in sign, and the heterozygote having a value determined by the gene and heterozygote frequencies. The model is specified in a canonical form which reveals the correlation between mates based on genotypic values, and relates the correlation to the fixation index. It permits negative as well as positive values of the fixation index. It is shown that this general model includes several particular cases, in equilibrium phase, occurring in the literature.

Alleles↗
PubMed1998

Male traits, mating tactics and reproductive success in the buff-breasted sandpiper, Tryngites subruficollis.

Buff-breasted sandpipers use a variety of mating tactics to acquire mates, including remaining at a single lek for most of the breeding season, attending multiple leks during the season, displaying solitarily or displaying both on leks and solitarily. We found that differences in body size, body condition, fluctuating asymmetry scores, wing coloration, territory location and behaviour (attraction, solicitation and agonistic) did not explain the observed variation in mating tactics used by males. Which males abandoned versus returned to leks was also not related to morphology or behaviour, and there was no tendency for males to join leks that were larger or smaller than the lek they abandoned. These results suggest that male desertion of leks was not dependent on a male's characteristics nor on the size of the lek he was presently attending. Males did join leks with larger males than their previous lek, perhaps to mate with females attracted to these larger 'hotshot' males. Males at both leks and solitary sites successfully mated. Lek tenure did not affect mating success, although lekking males appeared to mate more frequently than solitary males. Courtship disruption and to a lesser extent, female mimicry, were effective at preventing females from mating at leks, and may offer a partial explanation for female mating off leks. Our analysis that combined all males together within a year (regardless of mating tactic) indicated that males that attended leks for longer periods of time and that had fewer wing spots were significantly more likely to mate. Given some evidence that wing spotting declines with age, and that females inspect male underwings during courtship, the latter result suggests that female choice may play some role in determining male success. We suggest that male buff-breasted sandpipers may use alternative mating tactics more readily than males in other 'classic' lek-breeding species because: (1) unpredictable breeding conditions in this species' high arctic breeding range leads to low lek stability, which in turn hinders mate selection mechanisms mediated by male dominance and female choice; and (2) males are not constrained by morphological markings that indicate status or sex. Both characteristics may reduce the reproductive benefits associated with males adopting one mating tactic and result in a sort of scramble competition in which males switch between tactics as local conditions change.Copyright 1998 The Association for the Study of Animal Behaviour

Journal Article↗
PubMed1976

Assortative mating between chromosome forms of the mole rat, Spalax ehrenbergi.

Females of two parapatric chromosomal forms (2n = 52 and 2n =58) of the fossorial mole rat, Spalax ehrenbergi, in Israel, were tested for mate selection between two alternative, a homo- and a heterochromosomal, males. Estrous females significantly preferred the male of their own chromosomal form, on the basis of several behavioural criteria. The evolutionary significance of the positive assortative mating found, lies presumably in reinforcing reproductive isolation between the chromosome forms, thereby contributing to finalize speciation.

Animals↗
PubMed2000

Hormones and mating system affect sex and species differences in immune function among vertebrates.

Males generally exhibit reduced immune responses as well as increased intensity and prevalence of infections compared to female conspecifics. Physiologically, these sex differences may reflect the immunosuppressive effects of androgens. In addition to suppressing immune function, androgens maintain several characteristics important for reproductive success. Thus, a dynamic relationship is assumed to exist among hormones, secondary sex traits, and the immune system. Ultimately, the extent to which this relationship exists may be related to the mating system. Because polygynous males generally have higher circulating testosterone concentrations and rely more heavily on testosterone-dependent traits for reproductive success than monogamous males, sex differences in immune function are hypothesised to be more pronounced among polygynous as compared to monogamous species. Additionally, if secondary sex traits are used to advertise infection status, then females should be able to use the condition of male secondary sex traits to discern the immune/infection status of males during mate selection. The purpose of this review is to survey current studies that examine both the proximate mechanisms and ultimate function of variation in immune function and susceptibility to infection and determine whether immunological variation influences mate preference and possibly reproductive success.

Journal Article↗
PubMed1977

Comments on the Penrose-Stanton model of assortative mating.

A single-locus model of assortative mating proposed by Penrose and extended by Stanton is analysed. It is shown that the formulae giving values of correlations between males and relatives derived by Stanton apply to a general class of symmetric, non-selective mating schemes in equilibrium when genotypes have additive values. The canonical form of Stanton's system is derived, revealing that the assignment of additive values of genotypes does not apply also to the canonical vectors.

Crosses, Genetic↗
PubMed1998

Developmental isolation and subsequent adult behavior of Drosophila paulistorum. IV. Courtship.

Early social experiences play important roles in adult Drosophila paulistorum mate selection. Differences in courtship between control males and wholly socially isolated males were observed in chambers. Socially isolated males displayed more courtship toward virgin females than did controls. Socially isolated males were more successful in competing for mates. Yet socially isolated males from all six semispecies also displayed notable frequencies of homosexual behavior.

Analysis of Variance↗
PubMed2000

Fos expression in female hamsters after various stimuli associated with mating.

Detection of the expression of c-fos mRNA or its protein product, Fos, has been used to indicate differences in neuronal response to exogenous stimuli. Factors contributing to differences in Fos expression as a result of various stimuli associated with mating have been extensively studied in the female rat. Less is known about the factors that contribute to Fos expression in female hamsters. Female hamsters differ from female rats in several aspects of sexual behavior; therefore, it seems likely that Fos expression may also differ. The purpose of this study was to determine which factors associated with mating selectively affect Fos expression in the female hamster. Animals were ovariectomized, hormone treated, and then exposed to several behavioral conditions. Fos expression in several brain areas was then assessed via immunocytochemistry (ICC). As has been found by others, mating increases Fos immunoreactivity in a number of brain regions. Specifically, vaginal-cervical stimulation (VCS) was determined to be the salient factor contributing to Fos expression in the preoptic area (POA) and bed nucleus of the stria terminalis (BNST) of ovariectomized hormone primed female hamsters that received a mating interaction.

Animals↗
PubMed2000

Animal model of ethanol abuse: rats selectively bred for high and low voluntary alcohol intake.

The selectively bred alcohol-preferring and alcohol-non-preferring lines of rats have been used to study the biology of alcohol abuse and dependence. In our laboratory new lines of Wistar rats have been selectively outbread for 7 years and 19 generations for high and low ethanol intake (WHP--Warsaw High Preferring) and WLP--Warsaw Low Preferring respectively). After the first selection procedure, the highest scoring females and males were used initiate upward selection, while the lowest scoring pairs were used to initiate downward selection. Mated pairs were housed in breeding cages, pups were allowed to nurse for 3 weeks before weaning, then the pups of each litter were culled to the same-sex cage and allowed to mature until they were subjected to the selection procedure. In order to determine the alcohol intake and preference, the rats were individually housed in wire cages containing two graduated drinking tubes mounted at the front. During the entire investigation, the subjects had free access to standard lab chow (Bacutil, Poland). Ethanol solution was prepared from 95% stock ethanol and tap water. The animals were presented with 10% ethanol solution and water (two-bottle choice test). The drinking tubes were rotated daily to prevent position preference. Alcohol intake was calculated as average g/kg/day (absolute ethanol) while alcohol preference (in %) was calculated as the amount of alcohol consumed/total fluid x 100. Our results (17-19 generations) have shown that mean alcohol intake in WHP rats was higher than 5.0 g/kg/24 h ethanol, while WLP rats generally consumed less than 2.0 g/kg/24 h ethanol. Our results also showed that the total fluid intake in WHP rats slightly but not significantly higher as compared with WLP rats. Maximal ethanol consumption (in both lines) occurred during the natural dark phase three bungs (19.00-20.00 hrs, 23.00-02.00 hrs and 04.00-05.00 hrs). Interestingly, the intakes of high concentrations of sucrose and saccharin solutions were significantly higher in WHP than in WLP rats. Furthermore, the WHP rats reduced their alcohol and water intakes in the presence of 10% sucrose solution. Thus, it appears that high consumption of sweets may be a neurobiological factor promoting increased ethanol intake by WHP rats.

Alcohol Drinking↗
PubMed1997

The Hamilton-Zuk theory and initial test: an examination of some parasitological criticisms.

It has been supposed repeatedly that the Hamilton & Zuk paper of 1982 was parasitologically misconceived. These criticisms are shown to be inconsistent or mistaken. Various assumptions deemed unjustifiable by critics were either not made in the original paper, or have been made commonly, reasonably and pragmatically, by parasitologists themselves. The requirement by the theory for pathogenicity is examined, as is the need for the individuals to encounter the relevant parasites. The possible roles of parasite aggregation, parasites other than those directly involved, and costs of resistance, in making sosigonic selection less feasible are put into perspective. The rationale, interpretation and value of the preliminary comparative test with haematozoa are discussed. The advisability of incorporating host age, the location and timing of any sampling for parasites, and the actual ability of successful mates to resist disease is acknowledged. Attention is directed towards several specific observations. (1) It is a little recognised fact that Hamilton and Zuk assessed prevalence-showiness associations within surveys in restricted localities. (2) Many parasitological studies have not properly addressed the need to control for sampling effort when using prevalence data. (3) Contrary to some claims, the notion that haematozoa are sufficiently pathogenic is not unrealistic. (4) That non-resistant as well as resistant individuals might be free of patent or even latent infection at the time of mate choice was one of the possibilities mentioned originally. (5) In 1984, Eshel & Hamilton emphasised that environmental variation (whatever its source) has the potential to make mate selection for heritable characters based on perceptible variation less likely to evolve. (6) Hamilton & Zuk concluded that their findings "hint" that parasitism could be one agitator required for "good genes" sexual selection, a stance which is not immoderate. Lastly, the potential importance in evolutionary biology of parasite-mediated sexual selection as a form of co-evolution is considered briefly.

Host-Parasite Interactions↗
PubMed1990

The effect of intersubspecific hybridization and gamma radiation on the reproductive biology of Glossina palpalis palpalis (Robineau-Desvoidy) and Glossina palpalis gambiensis Vanderplank.

The closely related tsetse fly subspecies Glossina palpalis palpalis (Nigeria origin) and Glossina palpalis gambiensis (Burkina Faso origin) hybridize readily in the laboratory. Hybridized G.p.palpalis females produced less offspring than the parental intrasubspecific crosses. Adult emergence was below 70% with at least 78% being females. Most female hybrids were fertile whereas most of the male hybrids were sterile when backcrossed to the G.p.palpalis parental line. All F1 males were capable of transferring a spermatophore but their mates rarely had sperm-impregnated spermathecae. Their testes rarely contained mature sperm; moreover, sperm, when present had low or no motility. During laboratory cage tests with virgin females of both subspecies and either sexually mature male G.p.palpalis or G.p.gambiensis, there was no indication for selective mating. The same was true when gamma irradiated males (120 Gy treatment in air) were used. In the latter case complete sterility was induced causing embryonic arrest in all inseminated female mates. Consequently, in ratio tests with untreated virgin G.p.palpalis females, untreated G.p.palpalis males and an increasing number of irradiated G.p.gambiensis males, there was a gradual decrease in production of viable offspring. The results of the present study are discussed with a view of using a combined hybridization and induced sterility in distinct geographical zones where the two subspecies are present.

Animals↗