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At least 1,333 records · Page 74Linked to original sources
PubMed2004

Intra- and interspecific competition between biotypes B and Q of Bemisia tabaci (Hemiptera: Aleyrodidae) from Spain.

Biotypes B and Q of Bemisia tabaci (Gennadius), collected from the islands of Tenerife and Majorca respectively, were exposed to competition conditions on tomato cv. Marmande in the laboratory. Both biotypes were established in single and mixed cultures at different densities. Increased mortality of biotype Q females and immature instars was observed together with a lower rate of fecundity and progeny size compared to biotype B, when reared in single or mixed cultures. The female:male sex ratio of F1 individuals of biotype Q was higher in single than in mixed cultures. However, the sex ratio of F1 individuals of biotype B was the same in single and mixed cultures, suggesting reproductive interference. Whitefly density did not affect interspecific interactions. It had a moderate effect on developmental rate of both biotypes, and on mortality of immature instars and progeny size of biotype B only. The results indicate that under laboratory conditions the studied biotype B should displace biotype Q.

Animals↗
PubMed2005

Description and behavioural biology of two Ufens species (Hymenoptera: Trichogrammatidae), egg parasitoids of Homalodisca species (Hemiptera: Cicadellidae) in southern California.

The morphology, distribution, and hosts of two egg parasitoids, Ufens principalis Owen sp. n. and U. ceratus Owen sp. n. (Hymenoptera: Trichogrammatidae), are described for the first time. These species are compared to U. niger (Ashmead), the only species of Ufens s. str. currently described from the Nearctic, and diagnostic differences are presented. The behavioural biology of U. principalis, and U. ceratus to a smaller extent, is also described for the first time. Ufens principalis exhibited a rapid and long-distance response in the form of directional flight toward freshly laid eggs of Homalodisca species, its primary hosts in southern California. Parasitism involved aggregations of female U. principalis on fresh Homalodisca egg masses, which remained attractive to U. principalis for a relatively short time. The level of oviposition by U. principalis females was low during most of the day and peaked before sunset in tandem with a peak in Homalodisca oviposition. Oviposition behaviour of U. principalis is described and the distribution of ovipositor probe durations showed that most probes were generally of very short duration. Mating of both Ufens species occurred on the egg mass, with males showing aggressive behaviour towards each other as they competed for emerging females. Ufens ceratus males displayed greater aggression towards other males than U. principalis males. By contrast, fights among U. principalis males involved more individuals and lasted longer than corresponding fights between U. ceratus males.

Aggression↗
PubMed2003

Interactions between Schistosoma intercalatum (Zaire strain) and S. mansoni.

Schistosoma mansoni and S. intercalatum, two schistosomes from different evolutionary lineages, are parasitic in humans and therefore able to co-infect the same host where they occur sympatrically in Africa. Previous studies of mating interactions between these species in mice, using the Lower Guinea strain of S. intercalatum, have demonstrated the competitive dominance of S. mansoni over S. intercalatum in terms of pairing ability, which is potentially an important mechanism restricting the distribution of S. intercalatum in Africa. The study presented here examines the mating interactions in mice between S. mansoni and the Zaire (Democratic Republic of Congo) strain of S. intercalatum, which differs from the Lower Guinea strain in many biological characteristics. Analysis of the data showed a preponderance of intraspecific pairs over interspecific, demonstrating a specific mate preference system for both species. Mating competition between these species and the ability of males of both species to effect a change of mate by pulling paired females away from their partners was indicated. Comparisons are made between the competitive mating abilities of both strains of S. intercalatum relative to those of S. mansoni, with the data suggesting that S. mansoni is competitively dominant to S. intercalatum (Zaire) in sequential infections but to a lesser extent than for S. intercalatum (Lower Guinea). Additional factors which may contribute to the confinement of S. intercalatum (Zaire) to the Democratic Republic of Congo are discussed.

Animals↗
PubMed1999

Perceived control systems, work conditions, and efficiency among Swedish dentists: interaction between two sides of human resource management.

Two aspects of Human Resource Management (HRM), a main trend in modern personnel management, are considered in this study: A 'hard' version stressing performance monitoring and competition, and a 'soft' version stressing communication with employees. The aim of the investigation was to examine whether these two aspects of modern management are reflected in dentists' perceptions of differences in work conditions compared with other professionals. A questionnaire was answered by 312 publicly employed dentists and 3,600 other professionals in Sweden. The response rate was 66-77%. Effects from HRM on work, conditions and perceived efficiency were confirmed. The interaction effects, reflecting the duality of HRM, resulted in poorer work conditions, e.g. worse balance between effort and reward and worse opportunities for developing competence and collaboration in the workplace. This pertains especially in the case of dentists, where the positive effects of 'soft' HRM did not compensate for the negative effects of 'hard' HRM. Dentists in Sweden's Public Dental Health Service appear as a vulnerable group among Swedish professionals.

Attitude of Health Personnel↗
PubMed2004

Competition: how hypnosis can help women to hold their own in the workplace.

This paper takes the perspective that competitive strivings in self and others have been an area of difficulty for women and that gender socialization has played a significant role. The author discusses elements of competition that seem toxic for women and proposes descriptors of healthy competition. It is proposed that hypnosis provides a suitable method for neutralizing negative elements and promoting adaptive responses in competitive situations. Five applications of hypnotic methods are illustrated through two case examples.

Adaptation, Psychological↗
PubMed1991

Social hierarchies in very young chicks.

1. Three behavioural tests involving social competition were used to determine rank orders in groups of 8 male chicks aged between 4 and 18 days posthatching. 2. The group structure was found to consist of one or two dominant animals which consistently held a position at the top of the rank order, with a more flexible order beneath this. 3. Compared to the top-ranking birds, the middle- and lower-ranking birds showed more variability in their ranking positions across the behavioural tests and the testing periods. 4. Treatment of the lowest ranking individual in each group with testosterone led to this individual's rise in the rank order, most often to the top rank.

Animals↗
PubMed1994

Blood lead levels of British competitive cyclists.

This study examined the extent to which the potentially toxic lead particulates emitted from motor vehicles are absorbed by competitive cyclists. A time trial (n = 5), a road race (n = 5), and a sedentary control group (n = 5) were examined with respect to blood lead (PbB) levels. In the two cycling groups, the PbB levels were measured before and after (1) a time trial (80 km) held on a dual carriageway; and (2) a road race (120 km) which took place in a rural area. Mean (+/- SE) resting PbB levels for the sedentary subjects, time trialists, and road racers were 0.442 +/- 0.041, 0.490 +/- 0.111 and 0.384 +/- 0.061 mumol l-1 respectively (p > 0.05). Mean post-race PbB levels of the time trialists (0.528 +/- 0.046 mumol l-1) and road racers (0.346 +/- 0.024 mumol l-1) did not differ significantly from the pre-race levels (p > 0.05). However, after their respective races, the mean PbB level of the time trialists was higher than that of the road racers (p < 0.05). Ninety minutes of cycling (70% VO2 max) in a laboratory containing approximately 1 microgram m3 of airborne lead did not affect blood lead levels. All PbB levels compiled with EC regulations regarding lead exposure. Despite a positive relationship between the amount of training and the PbB levels (r = 0.64, p < 0.05), competitive cyclists did not evidence abnormal levels of lead absorption. Time trialing on dual carriageways was associated with higher PbB levels than road racing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Effect of alcohol and risk of physical harm on human physical aggression.

Forty male undergraduate students ingested either a high dose of alcohol or a placebo and were provided with feedback regarding their risk of receiving electric shock from an opponent in a competitive reaction-time situation. Intoxicated subjects (blood concentration of 96mg/dL) responded more aggressively than did the sober subjects on measures of physical aggression. Results indicated that the feedback manipulation had no effect on the aggressive responses of the intoxicated subjects. The findings are discussed in terms of current cognitive models of alcohol-related aggression.

Adolescent↗
PubMed1990

Interactions of preschool and kindergarten friends and acquaintances.

The interactions of 4-, 5-, and 6-year-old friends and acquaintances in a peer teaching and game-playing situation were examined. The sample consisted of 102 children who were divided into pairs of same-age, same-sex friends or acquaintances using sociometrics. One child in each pair was randomly chosen to be the teacher and the other the learner. The teachers taught a novel board game to the learners. The most common teaching method was a combination of explaining and demonstrating the rules before the game began; older children gave more comprehensive instructions than younger children. At all ages, teachers were more likely than learners to take the first turn, issue commands, and change the rules. Friends were rated more involved with their partners, more emotionally expressive, and more competitive than acquaintances. Teachers who taught friends were rated more domineering than teachers who taught acquaintances, and learners who were taught by friends were rated more playful and friendly than learners taught by acquaintances.

Child↗