Olympiad Festival of the Nations, 1936.
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Competitive Behavior↗
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A social component in the negative effect of sons on maternal longevity in pre-industrial humans.
Due to their effect on maternal testosterone levels, sons are said to have reduced maternal longevity in pre-industrial humans. This analysis, using information from a Flemish agricultural village in the 18th-20th centuries, confirms the presence of a negative effect of sons on maternal longevity. However, the effect is mainly observed for mothers belonging to the least privileged social group and for sons surviving their fifth birthday. Both findings make the above-mentioned biological explanation relative. However, a plausible alternative, social interpretation is male-dominated intra-household resource competition. It is reasonable to assume that only sons above a certain age are able to claim a serious amount of resources and that competition is strongest within the least privileged social group.
Belgium↗
Are gender differences in high achievement disappearing? A test in one intellectual domain.
Males traditionally predominate at upper achievement levels. One general view holds that this is due only to various social factors such as the 'glass ceiling' and lack of female role models. Another view holds that it occurs partly because of innate ability differences, with more males being at upper ability levels. In the last few decades, women have become more achievement focused and competitive and have gained many more opportunities to achieve. The present study examined one intellectual domain, international chess, to quantify its gender differences in achievement and to see if these have been diminishing with the societal changes. Chess is a good test domain because it is a meritocracy, it has objective performance measures, and longitudinal data of a whole population are available. Performance ratings overall and in the top 10, 50 and 100 players of each sex show large gender differences and little convergence over the past three decades, although a few females have become high achievers. The distribution of performance ratings on the January 2004 list shows a higher male mean and evidence for more male variation, just as with traits such as height. Career patterns of players first on the list between 1985 and 1989 show that top males and females entered the list at about the same age but females tend to play fewer games and have shorter careers. In this domain at least, the male predominance is large and has remained roughly constant despite societal changes.
Achievement↗
Intra- and interspecific density-dependent effects on growth in helminth parasites of the cormorant, Phalacrocorax carbo sinensis.
The action of intra- and interspecific competition, mediated by density-dependent effects on growth, was investigated among the 3 helminth species found in the alimentary tract of 104 cormorants, Phalacrocorax carbo sinensis. Intraspecific density-dependent effects on worm sizes were observed in the abundant nematode Contracaecum rudolphii, as shown by a negative correlation between mean worm size and intensity of infection. Higher intensities of infection by C. rudolphii were also associated with more variable worm sizes in the nematode Syncuaria squamata, suggesting a one-sided and density-dependent interspecific effect. There was also clear evidence of some form of negative interaction between the nematode S. squamata and the acanthocephalan Southwellina hispida from two fronts. First, there was a strong negative correlation between the intensities of infection of the 2 species across hosts. Second, sizes of worms of 1 species became more variable as the number of worms of the other species per host increased, and vice versa. This interspecific density-dependent effect on growth was thus apparently symmetrical. We also found evidence that worm size is a predictor of egg output in the 3 helminth species, indicating that intra- and interspecific density-dependent effects on growth can affect population dynamics in these worms. These results illustrate the complex nature of density dependence in helminth growth, and how its effects can act both within and among species.
Acanthocephala↗
The impact of a vertically transmitted microsporidian, Nosema granulosis on the fitness of its Gammarus duebeni host under stressful environmental conditions.
Although purely vertically transmitted parasites are predicted to cause low pathogenicity in their hosts, the effects of such parasites on host fitness under stressful environmental conditions have not previously been assessed. Here, we investigate the effects of Nosema granulosis, a vertically transmitted, microsporidian parasite of the brackish water amphipod Gammarus duebeni, on host growth and survival under conditions of host-host competition and limited food. The parasite had no effect on host survival, but caused a reduction in juvenile growth. Stressful environmental conditions also led to a reduction in G. duebeni growth. However, we found no evidence to support the prediction that parasitized hosts would suffer a greater reduction in fitness than uninfected hosts under adverse environmental conditions. We interpret our results in the context of selection for successful vertical parasite transmission.
Amphipoda↗
Muscles or testes? Comparative evidence for sexual competition among dioecious blood parasites (Schistosomatidae) of vertebrates.
Schistosomes, which live as parasitic adults in the blood vessels of mammals, birds and crocodiles, are unique among trematodes because they have separate sexes. Several studies have shown that the sex ratio is often biased towards males. Sexual dimorphism can be very important in several genera (Schistosoma, Heterobilharzia, Schistosomatium), as larger males grip smaller females in a gynecophoric canal. But not all schistomatid species have developed a gynecophoric canal. It is also striking that the number of testes varies widely, from a small number of testes reported (2-7) to a very high number (> 500). We tested the hypothesis of trade-off investment by males: muscle (as estimated by the length of the gynecophoric canal) in order to sequester one or a few females, or testes in order to inseminate numerous females. We used recent comparative methods, which need phylogenetic information of the analysed species. We employed a morphological cladistic analysis of the Schistosomatidae and a construction of a phylogenetic supertree of Schistosoma based on available molecular information. Our phylogenetic analysis supports previous hypotheses on the origin and diversification of the schistosomes. The family seems to have originated as parasites of crocodiles (or possibly other related poikilotherms) and to have secondarily evolved within the Aves and then mammals. Our phylogenetic analyses show that (1) the possession of a gynecophoric canal is a plesiomorphic character, and several reductions of this character have occurred during the diversification of the Schistosomatidae; (2) a small number of testes is a plesiomorphic stage, and an increase of testes number has occurred several times. Finally, our comparative analysis suggests that there is a trade-off between investment in muscle or in number of testes (other variables being controlled for). Male competition for access to females seems to follow two ways: investment in testes in order to fertilize a high number of females or investment in muscle in order to hold and sequester one (Schistosoma) or a few females (Heterobilharzia). We show the existence of the trade-off between muscles and testes in connection with a male biased sex ratio. The development of dioecy cannot explain the trade-off between muscles and testes, which instead appears to be a result of sexual selection possibly driven by the male biased sex ratio.
Alligators and Crocodiles↗
Sexual competition in an acanthocephalan parasite of fish.
Acanthocephalans are polygamous parasites of vertebrates and some species are known to aggregate in sexual congress to mate. Such a reproductive behaviour could lead to male-male competition for access to females and could have consequences for sexual selection. We dissected 87 gobiid fish, Gobius bucchichii, harbouring 891 acanthocephalans, Acanthocephaloides propinquus. The parasites were sexed and their body sizes were measured. Testicular volume was also evaluated in 82 males in order to establish their phenotypic sexual investment in relation to the estimated sex ratio. We found that parasite intensity (i.e. the number of individuals/fish) was not correlated with fish size, but that parasite size was significantly related to host size. Our results showed that there was a significant relationship between the mean female body size and their number within one host. We found that when the percentage of male parasites in a host increased, presumably increasing male-male competition for access to females, males had a larger testicular volume. We discuss these results in terms of energy allocation, sexual and sperm competition. We conclude that competition for space should be less important for males than competition for access to females. Moreover, increasing testis size should confer advantages to males especially for their reproductive success when sperm competition occurs.
Acanthocephala↗
Socio-cultural factors in the development of anorexia nervosa.
A population of professional dance (N = 183) and modelling (N = 56) students, who by career choice must focus increased attention and control over their body shapes, was studied. Height and weight data were obtained on all subjects. In addition, a questionnaire that is useful in assessing the symptoms of anorexia nervosa, the Eating Attitudes Test (EAT), was administered. Results of these tests were compared with those of normal female university students (N = 59), patients with anorexia nervosa (N = 68), and music students (N = 35). Anorexia nervosa and excessive dieting concerns were overrepresented in the dance and modelling students. Twelve cases (6.5%) of primary anorexia nervosa were detected in the dance group. All but one case developed the disorder while studying dance. Within the dance group those from the most competitive environments had the greatest frequency of anorexia nervosa. These data suggest that both pressures to be slim and achievement expectations are risk factors in the development of anorexia nervosa. The influence of socio-cultural determinants are discussed within the context of anorexia nervosa as a multidetermined disorder.
Anorexia Nervosa↗
Staying alive: evolution, culture, and women's intrasexual aggression.
Females' tendency to place a high value on protecting their own lives enhanced their reproductive success in the environment of evolutionary adaptation because infant survival depended more upon maternal than on paternal care and defence. The evolved mechanism by which the costs of aggression (and other forms of risk taking) are weighted more heavily for females may be a lower threshold for fear in situations which pose a direct threat of bodily injury. Females' concern with personal survival also has implications for sex differences in dominance hierarchies because the risks associated with hierarchy formation in nonbonded exogamous females are not offset by increased reproductive success. Hence among females, disputes do not carry implications for status with them as they do among males, but are chiefly connected with the acquisition and defence of scarce resources. Consequently, female competition is more likely to take the form of indirect aggression or low-level direct combat than among males. Under patriarchy, men have held the power to propagate images and attributions which are favourable to the continuance of their control. Women's aggression has been viewed as a gender-incongruent aberration or dismissed as evidence of irrationality. These cultural interpretations have "enhanced" evolutionarily based sex differences by a process of imposition which stigmatises the expression of aggression by females and causes women to offer exculpatory (rather than justificatory) accounts of their own aggression.
Aggression↗
Is the breadth of individualized ranges of optimal anxiety (IZOF) equal for all athletes? A graphical method for establishing IZOF.
Recall and direct methods to determine the individual zone of optimal functioning (IZOF) cannot account for potential individual differences in the span of optimal anxiety. Accordingly, an attempt was made to test a graphical technique that could establish the span of optimal anxiety ranges for individuals. State anxiety (STAI; Spielberger, Gorusch, & Lushene, 1970; and CSAI-2; Martens, Burton, Vealey, Bump, & Smith, 1990) was assessed before competitions (10 to 20) in six Spanish golfers during a season. Performance in each match was determined using golf scores and self-ratings. Optimal anxiety ranges were established graphically by plotting individual scores of precompetition anxiety against individual performance values. Optimal ranges were also determined using Hanin's (1986, 1989) direct and recall methods. The efficacy of each method was contrasted by comparing performance between cases in which the golfers possessed optimal or non-optimal anxiety according to each method. More of the golfers performed better when competing within an IZOF established with the graphic procedures than with the other methods.
Adolescent↗
Adhesion between molecules and calcium oxalate crystals: critical interactions in kidney stone formation.
Kidney stones are crystal aggregates, most commonly containing calcium oxalate monohydrate (COM) crystals as the primary constituent. Notably, in vitro studies have suggested that anionic molecules or macromolecules with substantial anionic functionality (e.g., carboxylate) play an important role in crystal aggregation and crystal attachment to renal epithelial cells. Furthermore, kidney stones contain measurable amounts of carboxylate-rich proteins that may serve as adhesives and promote aggregation of COM crystals. Atomic force microscopy (AFM) measurements of adhesion forces between tip-immobilized molecules and the COM (100) surface in aqueous media, described herein, reveal the effect of functional groups on adhesion and support an important role for the carboxylate group in processes responsible for kidney stone formation, specifically macromolecule-mediated adhesion of COM crystals to cells and crystal aggregation. The presence of poly(aspartic acid) during force measurements results in a reduction in the adhesion force measured for carboxylate-modified tips, consistent with the blocking of binding sites on the COM (100) surface by the carboxylate-rich polymer. This competitive binding behavior mimics the known reduction in attachment of COM crystals to renal epithelial cells in the presence of carboxylate-rich urinary macromolecules. These results suggest a feasible methodology for identifying the most important crystal surface-macromolecule combinations related to stone formation.
Calcium Oxalate↗
Intramolecular hydroamination/cyclization of conjugated aminodienes catalyzed by organolanthanide complexes. Scope, diastereo- and enantioselectivity, and reaction mechanism.
Organolanthanide complexes of the general type Cp'(2)LnCH(TMS)(2) (Cp' = eta(5)-Me(5)C(5); Ln = La, Sm, Y; TMS = SiMe(3)) and CGCSmN(TMS)(2) (CGC = Me(2)Si(eta(5)-Me(4)C(5))((t)()BuN)) serve as effective precatalysts for the rapid, regioselective, and highly diastereoselective intramolecular hydroamination/cyclization of primary and secondary amines tethered to conjugated dienes. The rates of aminodiene cyclizations are significantly more rapid than those of the corresponding aminoalkenes. This dienyl group rate enhancement as well as substituent group (R) effects on turnover frequencies is consistent with proposed transition state electronic demands. Kinetic and mechanistic data parallel monosubstituted aminoalkene hydroamination/cyclization, with turnover-limiting C=C insertion into the Ln-N bond to presumably form an Ln-eta(3) allyl intermediate, followed by rapid protonolysis of the resulting Ln-C linkage. The rate law is first-order in [catalyst] and zero-order in [aminodiene]. However, depending on the particular substrate and catalyst combination, deviations from zero-order kinetic behavior reflect competitive product inhibition or self-inhibition by substrate. Lanthanide ionic radius effects and ancillary ligation effects on turnover frequencies suggest a sterically more demanding Ln-N insertion step than in aminoalkene cyclohydroamination, while a substantially more negative DeltaS( double dagger ) implies a more highly organized transition state. Good to excellent diastereoselectivity is obtained in the synthesis of 2,5-trans-disubstituted pyrrolidines (80% de) and 2,6-cis-disubstituted piperidines (99% de). Formation of 2-(prop-1-enyl)piperidine using the chiral C(1)-symmetric precatalyst (S)-Me(2)Si(OHF)(CpR)SmN(TMS)(2) (OHF = eta(5)-octahydrofluorenyl; Cp = eta(5)-C(5)H(3); R = (-)-menthyl) proceeds with up to 71% ee. The highly stereoselective feature of aminodiene cyclization is demonstrated by concise syntheses of naturally occurring alkaloids, (+/-)-pinidine and (+)-coniine from simple diene precursors.
Journal Article↗
Lateral phase separation in adsorbed binary protein films at the air-water interface.
Lateral phase separation in two-dimensional mixed films of soy 11S/beta-casein, acidic subunits of soy 11 (AS11S)/beta-casein, and alpha-lactalbumin/beta-casein adsorbed at the air-water interface has been studied using an epifluorescence microscopy method. No distinct lateral phase separation was observed in the mixed protein films when they were examined after 24 h of adsorption from the bulk phase. However, when the soy 11S/beta-casein and AS11S/beta-casein films were aged at the air-water interface for 96 h, phase-separated regions of the constituent proteins were evident, indicating that the phase separation process was kinetically limited by a viscosity barrier against lateral diffusion. In these films, beta-casein always formed the continuous phase and the other globular protein the dispersed phase. The morphology of the dispersed patches was affected by the protein composition in the film. In contrast with soy 11S/beta-casein and AS11S/beta-casein films, no lateral phase separation was observed in the alpha-lactalbumin/beta-casein film at both low and high concentration ratios in the film. The results of these studies proved that proteins in adsorbed binary films exhibit limited miscibility, and the deviation of competitive adsorption behavior of proteins at the air-water interface from that predicted by the ideal Langmuir model (Razumovsky, L.; Damodaran, S. J. Agric. Food Chem. 2001, 49, 3080-3086) is in fact due to thermodynamic incompatibility of mixing of the proteins in the binary film. It is hypothesized that phase separation in adsorbed mixed protein films at the air-water and possibly oil-water interfaces of foams and emulsions might be a source of instability in these dispersed systems.
Adsorption↗
Influence of individual aggressiveness on the dynamics of competitive populations.
Two populations are subdivided into two categories of individuals (hawks and lows). Individuals fight to have access to a resource which is necessary for their survival. Conflicts occur between individuals belonging to the same population and to different populations. We investigate the long term effects of the conflicts on the stability of the community. The model is a set of ODE's with four variables corresponding to hawk and dove individuals of the two populations. Two time scales are considered. A fast time scale is used to describe frequent encounters and fightings between individuals trying to monopolize the resource. A slow time scale is used for the demography and the long term effects of encounters. We use aggregation methods in order to reduce this model into a system of two ODE's only for the total densities of the two populations which is found to be a classical Lotka-Volterra competition model. We study different cases of proportions of hawks and doves in both populations on the global coexistence and the mutual exclusion of the two populations. Pure dove tactics in both populations are unstable. In cases of mixed hawk and dove in both populations, there is coexistence. Pure dove or mixed hawk-dove tactics in one population can coexist with pure hawks in the other one when the costs of fightings between hawks are large enough.
Aggression↗
Interference competition set limits to the fundamental theorem of natural selection.
The relationship between Fisher's fundamental theorem of natural selection and the ecological environment of density regulation is examined. Using a linear model, it is shown that the theorem holds when density regulation is caused by exploitative competition and that the theorem fails with interference competition. In the latter case the theorem holds only at the limit of zero population density and/or at the limit where the competitively superior individuals cannot monopolize the resource. The results are discussed in relation to population dynamics and life history evolution, where evidence suggests that the level of interference competition in natural populations is so high that the fundamental theorem does not apply.
Animals↗
Improving male mating competitiveness and survival in the field for medfly, Ceratitis capitata (Diptera: Tephritidae) SIT programs.
The success of the sterile insect technique (SIT) depends critically upon mating between released sterilized males and wild females. In Hawaii, improvements in the efficiency of sterile males were attempted on two separate fronts--mating enhancement and survival improvement. In the former, two methods have been investigated--selective breeding and aromatherapy. In the latter, flies which survived in field cages for several days were selected and bred to produce progeny with enhanced survival ability compared to control flies. Regarding mating selection, standard laboratory-reared males that successfully mated with wild females in field cages were allowed to breed. F1 offspring were inbred, then the selection procedure was repeated for four additional cycles. In the aromatherapy procedure, laboratory-reared males were exposed to ginger root oil for several hours 1 day prior to testing in field cages. Compared to controls, the selected flies improved the mating competitiveness of male flies ca. 3-fold, irradiation reduced this increase to ca. 2.5-fold. Exposing the selected, hybrid strain raised the fitness of the lab males to ca. 9-fold that of wild males. In the ongoing survival selection study, we have obtained lines in which the selected males survived ca. 2-fold better than laboratory control males over several days in an outdoor field cage, with food and water provided. The goal is to combine the traits of higher survival and mating ability into a single strain for SIT release.
Animals↗
An optimization model of competition between species for resource.
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Animals↗
Surgical research and the ethics of being first.
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Competitive Behavior↗