Floral trait variation across individual plants within a population enhances defense capability to nectar robbing.

Floral trait variation may help pollinators and nectar robbers identify their target plants and, thus, lead to differential selection pressure for defense capability against floral antagonists. However, the effect of floral trait variation among individuals within a population on multi-dimensional plant-animal interactions has been little explored. We investigated floral trait variation, pollination, and nectar robbing among individual plants in a population of the bumble bee-pollinated plant, Caryopteris divaricata, from which flowers are also robbed by bumble bees with varying intensity across individuals. We measured the variation in corolla tube length, nectar volume and sugar concentration among individual plants, and evaluated whether the variation were recognized by pollinators and robbers. We investigated the influence of nectar robbing on legitimate visitation and seed production per fruit. We found that the primary nectar robber (Bombus nobilis) preferred to forage on plants with long-tubed flowers, which produced less nectar and had lower sugar concentration compared to those with shorter corolla tubes. Individuals with shorter corolla tubes had comparatively lower nectar robbing intensity but higher visitation by legitimate visitors (mainly B. picipes) and higher seed production. Nectar robbing significantly reduced seed production because it decreased pollinator visits. However, neither pollination nor seed production differed between plants with long and short corolla tubes when nectar robbers were excluded. This finding suggests that floral trait variation might not be driven by pollinators. Such variation among individual plants thus allows legitimate visitors and nectar robbers to segregate niches and enhances population defense against nectar robbing in unpredictable conditions.

Prevalence and associated factors of depressive symptoms among Chinese doctors: a cross-sectional survey.

OBJECTIVES: Doctors, the major workforce in hospitals, are doing heavy emotional and physical work which may lead to depressive symptoms. However, in China, few studies are available pertaining to the prevalence and associated factors of depressive symptoms among doctors. The aim of this study was to evaluate the prevalence of depressive symptoms and to explore its associated factors among Chinese doctors in public hospitals. METHODS: This cross-sectional study was performed during the period of September/October 2008. The study population comprised of 1,890 doctors registered and working in the 20 national hospitals in Liaoning province, northeast of China. A questionnaire that comprised depressive symptoms assessed by the Chinese Version of the Center for Epidemiologic Studies Depression Scale (CES-D), demographic factors, work conditions, occupational stress, and coping strategies was distributed to these doctors. A total of 1,488 effective respondents became our subjects (effective response rate 78.7%). Multivariate logistic regression was used to explore the factors related to depressive symptoms. RESULTS: The prevalence of depressive symptoms among doctors was 65.3%. Multivariate logistic analyses showed that high role insufficiency (OR 2.15, 95% CI 1.66-2.78), worse doctor-patient relationship (OR 2.07, 95% CI 1.62-2.64), having a chronic disease (OR 1.73, 95% CI 1.31-2.27), serious role boundary (OR 1.54, 95% CI 1.21-2.00), and role overload (OR 1.42, 95% CI 1.11-1.81) were positively associated with depressive symptoms; whereas adequate rational coping (OR 0.58, 95% CI 0.45-0.76) and social support (OR 0.75, 95% CI 0.57-0.98) were negatively associated with depressive symptoms. CONCLUSIONS: Most Chinese doctors probably have depressive symptoms. Role insufficiency, doctor-patient relationship, and rational coping seemed to be crucial in relation to depressive symptoms. Efficient interventions such as taking further education course, improving communications with patients, and improving the ability of rational coping should be considered by health administrators aiming at improving the quality of Chinese doctors' mental health from the view point of depressive symptoms.

Occupational stress among hospital nurses: cross-sectional survey.

AIM: This paper is a report of a study conducted to explore factors associated with occupational stress among female hospital nurses in China. BACKGROUND: Nursing is a highly stressful occupation, and high levels of occupational stress are believed to affect the physical and mental health of nurses. Occupational stress among nurses is the result of exposure to a combination of working environment and personal factors. METHOD: A cross-sectional study was conducted in 2008. The study population consisted of 2613 female nurses from 20 hospitals in the Liaoning province of China. Occupational stress was measured by questionnaires that included the Chinese version of Personal Strain Questionnaire, and data were collected on respondents' demographics, working situations, occupational roles, and personal resources. Of the nurses solicited for enrolment in the study, 79.2% returned the completed questionnaire. A general linear regression model was applied to analyse the factors associated with occupational stress. RESULTS: Mean Personal Strain Questionnaire score was 86.9, and this score was correlated, in descending order of standardized estimate, with role boundary, role insufficiency, responsibility, social support, self-care, nurse-patient relationship, chronic disease, role overload, rational coping and night shift. CONCLUSION: Role boundary and role insufficiency were the factors that had the highest association with occupational stress. Occupational health education and occupational training programmes may be necessary to improve the knowledge and ability of nurses to cope with job demands and reduce occupational stress.

Change of floral orientation within an inflorescence affects pollinator behavior and pollination efficiency in a bee-pollinated plant, Corydalis sheareri.

Vertical raceme or spike inflorescences that are bee-pollinated tend to present their flowers horizontally. Horizontal presentation of flowers is hypothesized to enhance pollinator recognition and pollination precision, and it may also ensure greater consistency of pollinator movement on inflorescences. We tested the hypotheses using bee-pollinated Corydalis sheareri which has erect inflorescences consisting of flowers with horizontal orientation. We altered the orientation of individual flowers and prepared three types of inflorescences: (i) unmanipulated inflorescences with horizontal-facing flowers, (ii) inflorescences with flowers turned upward, and (iii) inflorescences with flowers turned downward. We compared number of inflorescences approached and visited, number of successive probes within an inflorescence, the direction percentage of vertical movement on inflorescences, efficiency of pollen removal and seed production per inflorescence. Deviation from horizontal orientation decreased both approaches and visits by leafcutter bees and bumble bees to inflorescences. Changes in floral orientation increased the proportion of downward movements by leafcutter bees and decreased the consistency of pollinator movement on inflorescences. In addition, pollen removal per visit and seed production per inflorescence also declined with changes of floral orientation. In conclusion, floral orientation seems more or less optimal as regards bee behavior and pollen transfer for Corydalis sheareri. A horizontal orientation may be under selection of pollinators and co-adapt with other aspects of the inflorescence and floral traits.