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1.
Cheptou PO 《Annals of botany》2012,109(3):633-641
Background
Baker''s Law states that colonization by self-compatible organisms is more likely to be successful than colonization by self-incompatible organisms because of the ability for self-compatible organisms to produce offspring without pollination agents. This simple model has proved very successful in plant ecology and has been applied to various contexts, including colonizing or ruderal species, islands colonizers, invasive species or mating system variation across distribution ranges. Moreover, it is one of the only models in population biology linking two traits of major importance in ecology, namely dispersal and mating system. Although Baker''s Law has stimulated a large number of empirical studies reporting the association of self-fertilization and colonizing ability in various contexts, the data have not established a general pattern for the association of traits.Scope
In this paper, a critical position is adopted to discuss and clarify Baker''s Law. From the literature referring to Baker''s Law, an analysis made regarding how mating success is considered in such studies and discrepancies with population genetics theory of mating systems are highlighted. The data reporting the association of self-fertilization and colonizing ability are also briefly reviewed and the potential bias in interpretation is discussed. Lastly, a recent theoretical model analysing the link between colonizing ability and self-fertilization is considered.Conclusions
Evolutionary predictions are actually more complex than Baker''s intuitive arguments. It appears that Baker''s Law encompasses a variety of ecological scenarios, which cannot be considered a priori as equivalent. Questioning what has been considered as self-evident for more than 50 years seems a reasonable objective to analyse in-depth dispersal and mating system traits. 相似文献2.
Purpose
To investigate whether social interactions in friendship networks influence the following weight-related behaviors of adolescents: exercising regularly, playing an active sport, hours of TV/Video viewing, sleeping six or fewer hours, eating breakfast on weekdays, frequency of eating at fast food restaurants, eating five servings of fruits/vegetables daily, and consuming calorie-dense snacks.Method
Data from a nationally representative sample of adolescents are used to examine the association between peer and individual weight-related behaviors. Evidence from multivariate regression analysis controlling for an extensive list of individual- and family-level factors as well as school-level unobserved heterogeneity is obtained.Results
We find a significant positive association between individuals'' and friends'' behaviors in terms of sports, exercise and fast food consumption. The estimated associations are robust to controls for individual- and family-level factors, unobserved heterogeneity at the school level and our attempts to account for non-random peer selection.Conclusions
The social transmission of weight-related behaviors is a viable explanation for the spread of obesity in friendship networks documented in recent research. Traditional weight reduction interventions may be fruitfully complemented with strategies that focus on harnessing peer support to modify behaviors. 相似文献3.
Background
Many extant male animals exhibit exaggerated body parts for display, defense or offence in sexual selection, such as male birds of paradise showing off colorful and elegant feathers and male moose and reindeers bearing large structured antlers. For insects, male rhinoceros and stag beetles have huge horn-like structure for fighting and competition and some male Leptopanorpa scorpionflies have very long abdominal terminal segments for sexual display and competition. Fossil records of insects having exaggerated body parts for sexual display are fairly rare. One example is two male holcorpids with elongate abdominal segments from sixth (A6) to eighth (A8) and enlarged male genitalia from Eocene, suggesting evolution of these characters occurred fairly late.Principal Findings
We document two mecopterans with exaggerated male body parts from the late Middle Jurassic Jiulongshan Formation in northeastern China. Both have extremely extended abdominal segments from A6 to A8 and enlarged genitalia, which might have been used for sexual display and, to less extent, for fighting with other males in the competition for mates. Although Fortiholcorpa paradoxa gen. et sp. nov. and Miriholcorpa forcipata gen. et sp. nov. seem to have affinities with Holcorpidae, we deem both as Family Incertae sedis mainly due to significant differences in branching pattern of Media (M) veins and relative length of A8 for F. paradoxa, and indiscernible preservation of 5-branched M veins in hind wing for M. forcipata.Conclusions/Significance
These two new taxa have extended the records of exaggerated male body parts of mecopterans for sexual display and/or selection from the Early Eocene to the late Middle Jurassic. The similar character present in some Leptopanorpa of Panorpidae suggests that the sexual display and/or sexual selection due to extremely elongated male abdominal and sexual organs outweigh the negative impact of bulky body and poor mobility in the evolutionary process. 相似文献4.
Background
The necessity of postural restriction to patients suffering from benign paroxysmal positional vertigo is controversial.Objective
To investigate the impact of the sleep position after the repositioning maneuver on BPPV recurrence.Methods
150 unilateral BPPV patients who were treated by repositioning maneuver were distributed into two groups. The patients in group A were instructed to sleep in a semi-sitting position at an angle of approximately 30 degrees and refrain from sleeping on their BPPV affected side for one week. The patients in group B were told to sleep in any preferred position. The comparison of recurrence rates according to different actual sleep positions in one week and one month was performed.Results
There was a statistically significant correlation between the sleeping side and the side affected by BPPV. Without instructions on postural restriction, most patients (82.9%, 73/88) avoided sleeping on their affected side. The patients sleeping on their affected side had a higher recurrence rate (35.3%) than ones sleeping in other positions in the first week after the repositioning maneuver (p<0.05, Chi-square test and Fisher''s exact test). The patients sleeping randomly in following 3 weeks had a lower recurrence rate than ones sleeping in other position (p<0.05, Fisher''s exact test).Conclusions
BPPV patients had a poor compliance to postural instructions. The habitual sleep side was associated with the side affected by BPPV. The patients sleeping on their affected side had a higher recurrence rate than those sleeping in other positions in first week after the repositioning maneuver. 相似文献5.
6.
Mascha K. Rochat Ruediger P. Laubender Daniela Kuster Otto Braendli Alexander Moeller Ulrich Mansmann Erika von Mutius Johannes Wildhaber 《PloS one》2013,8(1)
Background
Spirometry reference values are important for the interpretation of spirometry results. Reference values should be updated regularly, derived from a population as similar to the population for which they are to be used and span across all ages. Such spirometry reference equations are currently lacking for central European populations.Objective
To develop spirometry reference equations for central European populations between 8 and 90 years of age.Materials
We used data collected between January 1993 and December 2010 from a central European population. The data was modelled using “Generalized Additive Models for Location, Scale and Shape” (GAMLSS).Results
The spirometry reference equations were derived from 118''891 individuals consisting of 60''624 (51%) females and 58''267 (49%) males. Altogether, there were 18''211 (15.3%) children under the age of 18 years.Conclusion
We developed spirometry reference equations for a central European population between 8 and 90 years of age that can be implemented in a wide range of clinical settings. 相似文献7.
Background
According to sexual conflict theory, males can increase their own fitness by transferring substances during copulation that increase the short-term fecundity of their mating partners at the cost of the future life expectancy and re-mating capability of the latter. In contrast, sexual cooperation is expected in social insects. Mating indeed positively affects life span and fecundity of young queens of the male-polymorphic ant Cardiocondyla obscurior, even though males neither provide nuptial gifts nor any other care but leave their mates immediately after copulation and die shortly thereafter.Principal Findings
Here, we show that mating with winged disperser males has a significantly stronger impact on life span and reproductive success of young queens of C. obscurior than mating with wingless fighter males.Conclusions
Winged males are reared mostly under stressful environmental conditions, which force young queens to disperse and found their own societies independently. In contrast, queens that mate with wingless males under favourable conditions usually start reproducing in the safety of the established maternal nest. Our study suggests that males of C. obscurior have evolved mechanisms to posthumously assist young queens during colony founding under adverse ecological conditions. 相似文献8.
Background and Aims
Most research on the widespread phenomenon of nectar robbing has focused on the effect of the nectar robbers'' behaviour on host-plant fitness. However, attention also needs be paid to the characteristics of host plants, which can potentially influence the consequences of nectar robbing as well. A system of three sympatric Corydalis species sharing the same nectar-robbing bumble-bee was therefore studied over 3 years in order to investigate the effect of nectar robbing on host reproductive fitness.Methods
Three perennial species of Corydalis were studied in the Shennongjia Mountain area, central China. Observations were conducted on visitor behaviour and visitation frequencies of nectar-robbers and legitimate pollinators.Key Results
The results indicated that the effect of nectar robbing by Bombus pyrosoma varied among species, and the three species had different mating systems. Seed set was thus influenced differentially: there was no effect on seed set of the predominantly selfing C. tomentella; for the facultative outcrossing C. incisa, nectar robbing by B. pyrosoma had a positive effect; and nectar robbing had a significant negative effect on the seed set of outcrossing C. ternatifolia.Conclusions
A hypothesis is proposed that the type of host-plant mating system could influence the consequences of nectar robbing on host reproductive fitness.Key words: Nectar robbing, Corydalis, reproductive fitness, bumble-bee, Bombus pyrosoma, mating systems 相似文献9.
Eileen V. Pitpitan Seth C. Kalichman Demetria Cain Lisa A. Eaton Kate B. Carey Michael P. Carey Ofer Harel Leickness C. Simbayi Vuyelwa Mehlomakhulu Kelvin Mwaba 《PloS one》2012,7(10)
Background
Women in South Africa are at particularly high-risk for HIV infection and are dependent on their male partners'' use of condoms for sexual risk reduction. However, many women are afraid to discuss condoms with male partners, placing them at higher risk of HIV infection.Purpose
To examine the association between fear of condom negotiation with HIV testing and transmission risk behaviors, including alcohol use and sexual risks among South African women.Method
Women (N = 1333) residing in a primarily Xhosa-speaking African township in Cape Town and attending informal alcohol-serving venues (shebeens) completed anonymous surveys. Logistic regression was used to test the hypothesis that fear of condom negotiation would be associated with increased risk for HIV.Results
Compared to women who did not fear condom negotiation, those who did were significantly less likely to have been tested for HIV, were more likely to have experienced relationship abuse, and to report more alcohol use and more unprotected sex.Conclusions
For women in South Africa, fear of condom negotiation is related to higher risk of HIV. HIV prevention efforts, including targeted HIV counseling and testing, must directly address gender issues. 相似文献10.
Background
Members of the subfamily Galleriinae have adapted to different selective environmental pressures by devising a unique mating process. Galleriinae males initiate mating by attracting females with either chemical or acoustic signals (or a combination of both modalities). Six compounds considered candidates for the sex pheromone have recently been identified in the wing gland extracts of Aphomia sociella males. Prior to the present study, acoustic communication had not been investigated. Signals mediating female attraction were likewise unknown.Methodology/Principal Findings
Observations of A. sociella mating behaviour and recordings of male acoustic signals confirmed that males initiate the mating process. During calling behaviour (stationary wing fanning and pheromone release), males disperse pheromone from their wing glands. When a female approaches, males cease calling and begin to produce ultrasonic songs as part of the courtship behaviour. Replaying of recorded courting songs to virgin females and a comparison of the mating efficiency of intact males with males lacking tegullae proved that male ultrasonic signals stimulate females to accept mating. Greenhouse experiments with isolated pheromone glands confirmed that the male sex pheromone mediates long-range female attraction.Conclusion/Significance
Female attraction in A. sociella is chemically mediated, but ultrasonic communication is also employed during courtship. Male ultrasonic songs stimulate female sexual display and significantly affect mating efficiency. Considerable inter-individual differences in song structure exist. These could play a role in female mate selection provided that the female''s ear is able to discern them. The A. sociella mating strategy described above is unique within the subfamily Galleriinae. 相似文献11.
Background and Aims
Understanding patterns of pollen dispersal and variation in mating systems provides insights into the evolutionary potential of plant species and how historically rare species with small disjunct populations persist over long time frames. This study aims to quantify the role of pollen dispersal and the mating system in maintaining contemporary levels of connectivity and facilitating persistence of small populations of the historically rare Acacia woodmaniorum.Methods
Progeny arrays of A. woodmaniorum were genotyped with nine polymorphic microsatellite markers. A low number of fathers contributed to seed within single pods; therefore, sampling to remove bias of correlated paternity was implemented for further analysis. Pollen immigration and mating system parameters were then assessed in eight populations of varying size and degree of isolation.Key Results
Pollen immigration into small disjunct populations was extensive (mean minimum estimate 40 % and mean maximum estimate 57 % of progeny) and dispersal occurred over large distances (≤1870m). Pollen immigration resulted in large effective population sizes and was sufficient to ensure adaptive and inbreeding connectivity in small disjunct populations. High outcrossing (mean tm = 0·975) and a lack of apparent inbreeding suggested that a self-incompatibility mechanism is operating. Population parameters, including size and degree of geographic disjunction, were not useful predictors of pollen dispersal or components of the mating system.Conclusions
Extensive long-distance pollen dispersal and a highly outcrossed mating system are likely to play a key role in maintaining genetic diversity and limiting negative genetic effects of inbreeding and drift in small disjunct populations of A. woodmaniorum. It is proposed that maintenance of genetic connectivity through habitat and pollinator conservation will be a key factor in the persistence of this and other historically rare species with similar extensive long-distance pollen dispersal and highly outcrossed mating systems. 相似文献12.
Context
Prior research has faulted the US News and World Report hospital specialty rankings for excessive reliance on reputation, a subjective measure of a hospital''s performance.Objective
To determine whether and to what extent reputation correlates with objective measures of research productivity among cancer hospitals.Design
A retrospective observational study.Setting
Automated search of NIH Reporter, BioEntrez, BioMedline and Clinicaltrials.gov databases.Participants
The 50 highest ranked cancer hospitals in 2013''s US News and World Report Rankings.Exposure
We ascertained the number of NCI funded grants, and the cumulative funds received by each cancer center. Additionally, we identified the number of phase I, phase II, and phase III studies published and indexed in MEDLINE, and registered at clinicaltrials.gov. All counts were over the preceding 5 years. For published articles, we summed the impact factor of the journals in which they appeared. Trials were attributed to centers on the basis of the affiliation of the lead author or study principal investigator.Main Outcome
Correlation coefficients from simple and multiple linear regressions for measures of research productivity and a center''s reputation.Results
All measures of research productivity demonstrated robust correlation with reputation (mean r-squared = 0.65, median r-squared = 0.68, minimum r-squared = .41, maximum r-squared = 0.80). A multivariable model showed that 93% of the variation in reputation is explained by objective measures.Conclusion
Contrary to prior criticism, the majority of reputation, used in US News and World Rankings, can be explained by objective measures of research productivity among cancer hospitals. 相似文献13.
Background and Aims
Peripheral populations of plant species are often characterized by low levels of genetic diversity as a result of genetic drift, restricted gene flow, inbreeding and asexual reproduction. These effects can be exacerbated where range-edge populations are fragmented. The main aim of the present study was to assess the levels of genetic diversity in remnant populations of Hypopitys monotropa (syn. Monotropa hypopitys; yellow bird''s nest) at the edge of the species'' European range in Northern Ireland, since these remnant populations are small and highly fragmented.Methods
Every plant found through surveys of 21 extant populations was genotyped for eight microsatellite loci to estimate levels and patterns of genetic diversity and clonality.Key Results
Levels of genetic diversity were relatively high in the populations studied, and the incidence of clonal reproduction was generally low, with a mean of only 14·45 % of clonal individuals. Clones were small and highly spatially structured. Levels of inbreeding, however, were high.Conclusions
The observed low levels of clonality suggest that the majority of genets in the populations of H. monotropa studied are fertile and that reproduction is predominantly sexual. As the species is highly self-compatible, it is likely that the high levels of inbreeding observed in the populations in the present study are the result of self-pollination, particularly given the small numbers of individuals in most of the patches. Given this extent of inbreeding, further genetic monitoring would be advisable to ensure that genetic diversity is maintained. 相似文献14.
Background
Positive self-esteem, emotional well-being, school achievements and family connectedness are considered protective factors against health-compromising behaviors.This study examined the effect of an interactive, community-based, media literacy and dissonance wellness program, In Favor of Myself, on the self-image, body image, eating attitudes and behavior of young adolescents. A preliminary cohort study was conducted among 972 program participants who did not take part in the controlled trial. Over 75% of participants said they would recommend the program to their friends.Methods
A controlled trial was conducted to evaluate program acceptability, efficacy and effectiveness among 259 participants (210 in the intervention group and 49 in the control group), aged 12–14 years, who completed questionnaires during at least two assessment times. Program materials were provided, along with leaders'' training, in order to ensure quality program delivery and creation of a wide network of committed program leaders.Results
The program significantly reduced drive for thinness and self-worth contingent upon others'' approval, the gap between current body figure and ideal figure, and the impact of mood on girls'' self-image. Superiority was found among those participating in the intervention group with respect to recognizing media strategies, the influence of media on desire to change, and the influence of appearance on self-confidence and drive for thinness.Conclusions
In Favor of Myself shows promising results for strengthening adolescents'' ability to cope with the challenges of their life stage. Suggestions for improving In Favor of Myself are presented. 相似文献15.
Background
Multiple mating by female insects is widespread, and the explanation(s) for repeated mating by females has been the subject of much discussion. Females may profit from mating multiply through direct material benefits that increase their own reproductive output, or indirect genetic benefits that increase offspring fitness. One particular direct benefit that has attracted significant attention is that of fertility assurance, as females often need to mate multiply to achieve high fertility. This hypothesis has never been tested in a wild insect population.Methodology/Principal Findings
Female Malaysian stalk-eyed flies (Teleopsis dalmanni) mate repeatedly during their lifetime, and have been shown to be sperm limited under both laboratory and field conditions. Here we ask whether receiving an additional mating alleviates sperm limitation in wild females. In our experiment one group of females received a single additional mating, while a control group received an interrupted, and therefore unsuccessful, mating. Females that received an additional mating did not lay more fertilised eggs in total, nor did they lay proportionately more fertilised eggs. Female fertility declined significantly through time, demonstrating that females were sperm limited. However, receipt of an additional mating did not significantly alter the rate of this decline.Conclusions/Significance
Our data suggest that the fertility consequences of a single additional mating were small. We discuss this effect (or lack thereof), and suggest that it is likely to be attributed to small ejaculate size, a high proportion of failed copulations, and the presence of X-linked meiotic drive in this species. 相似文献16.
Background and Aims
Sexually deceptive orchids achieve cross-pollination by mimicking the mating signals of female insects, generally hymenopterans. This pollination mechanism is often highly specific as it is based primarily on the mimicry of mating signals, especially the female sex pheromones of the targeted pollinator. Like many deceptive orchids, the Mediterranean species Ophrys arachnitiformis shows high levels of floral trait variation, especially in the colour of the perianth, which is either green or white/pinkinsh within populations. The adaptive significance of perianth colour polymorphism and its influence on pollinator visitation rates in sexually deceptive orchids remain obscure.Methods
The relative importance of floral scent versus perianth colour in pollinator attraction in this orchid pollinator mimicry system was evaluated by performing floral scent analyses by gas chromatography-mass spectrometry (GC-MS) and behavioural bioassays with the pollinators under natural conditions were performed.Key Results
The relative and absolute amounts of behaviourally active compounds are identical in the two colour morphs of O. arachnitiformis. Neither presence/absence nor the colour of the perianth (green versus white) influence attractiveness of the flowers to Colletes cunicularius males, the main pollinator of O. arachnitiformis.Conclusion
Chemical signals alone can mediate the interactions in highly specialized mimicry systems. Floral colour polymorphism in O. arachnitiformis is not subjected to selection imposed by C. cunicularius males, and an interplay between different non-adaptive processes may be responsible for the maintenance of floral colour polymorphism both within and among populations. 相似文献17.
Background
The communicative meaning of human areolae for newborn infants was examined here in directly exposing 3-day old neonates to the secretion from the areolar glands of Montgomery donated by non related, non familiar lactating women.Methodology/Principal Findings
The effect of the areolar stimulus on the infants'' behavior and autonomic nervous system was compared to that of seven reference stimuli originating either from human or non human mammalian sources, or from an arbitrarily-chosen artificial odorant. The odor of the native areolar secretion intensified more than all other stimuli the infants'' inspiratory activity and appetitive oral responses. These responses appeared to develop independently from direct experience with the breast or milk.Conclusion/Significance
Areolar secretions from lactating women are especially salient to human newborns. Volatile compounds carried in these substrates are thus in a position to play a key role in establishing behavioral and physiological processes pertaining to milk transfer and production, and, hence, to survival and to the early engagement of attachment and bonding. 相似文献18.
Background
Eyewitness recalls and accident records frequently do not mention the conditions and behaviors of interest to researchers and lead to missing values and to uncertainty about the prevalence of these conditions and behaviors surrounding accidents. Missing values may occur because eyewitnesses report the presence but not the absence of obvious clues/accident features. We examined this possibility.Methodology/Principal Findings
Participants watched car accident videos and were asked to recall as much information as they could remember about each accident. The results showed that eyewitnesses were far more likely to report the presence of present obvious clues than the absence of absent obvious clues even though they were aware of their absence.Conclusions
One of the principal mechanisms causing missing values may be eyewitnesses'' tendency to not report the absence of obvious features. We discuss the implications of our findings for both retrospective and prospective analyses of accident records, and illustrate the consequences of adopting inappropriate assumptions about the meaning of missing values using the Avaluator Avalanche Accident Prevention Card. 相似文献19.
Thomas H. Riess Maryline M. Achieng’ Samuel Otieno J. O. Ndinya-Achola Robert C. Bailey 《PloS one》2010,5(8)
Background
Male circumcision has been shown to reduce the transmission of HIV from women to men through vaginal sex by approximately 60%. There is concern that men may engage in risk compensation after becoming circumcised, diminishing the benefits of male circumcision.Methods and Findings
We conducted qualitative interviews with 30 sexually active circumcised men in Kisumu, Kenya from March to November 2008. Most respondents reported no behavior change or increasing protective sexual behaviors including increasing condom use and reducing the number of sexual partners. A minority of men reported engaging in higher risk behaviors either not using condoms or increasing the number of sex partners. Circumcised respondents described being able to perform more rounds of sex, easier condom use, and fewer cuts on the penis during sex.Conclusions
Results illustrate that information about MC''s protection against HIV has disseminated into the larger community and MC accompanied by counseling and HIV testing can foster positive behavior change and maintain sexual behavior. 相似文献20.