Predicted Outcome (predicted + outcome)

Distribution by Scientific Domains


Selected Abstracts


Infrequent sporophyte production maintains a female-biased sex ratio in the unisexual clonal moss Hylocomium splendens

JOURNAL OF ECOLOGY, Issue 5 2010
Knut Rydgren
Summary 1.,Sex ratios in unisexual bryophytes are most often female biased, whereas male-biased sex ratios predominate in unisexual seed plants. This ,bryophyte paradox', i.e. that sex ratios are biased in favour of the sex associated with the highest reproductive costs, has remained unexplained. 2.,Analysis of sex-ratio patterns via the influence of sex distribution on population growth rates (,) has not previously been carried out for bryophytes. We used this method to model how variation in sex ratio and sporophyte frequency influences , in the clonal bryophyte Hylocomium splendens. We obtained , by matrix modelling of synthetic experimental populations derived from demographic field data, using a linear two-sex model. 3.,In our set of experimental populations , varied between 1.13 and 1.27 in response to variation in sex ratio and sporophyte frequency, with the highest , obtained for the combination of a very low sporophyte frequency and a slightly female-biased sex ratio. 4.,Our results explain the female-biased sex ratio of H. splendens by the slightly lower survival of and production of vegetative offspring by males than by non-sporophytic females. 5.,Synthesis. According to our models, female dominance is the predicted outcome of low to moderate fertilization success and male performance intermediate between that of sporophytic and of non-sporophytic females. Our results therefore explain how a female-biased sex ratio can be maintained despite higher costs of reproduction in females than in males. In dioecious bryophytes, males and females must grow in close contact for fertilization to take place. Better performance of male ramets than of the female ramets they fertilize also explains how male clones can expand into female clones. A similar performance hierarchy of males and females may occur in unisexual clonal seed plants, but more efficient fertilization systems by pollination prevents the selective advantage of unfertilized females from being realized. This explains why vascular plant populations tend to be male biased. We hypothesise difference in fertilization distance range between sperm and pollen as a simple explanation why ramet level sex ratios are in general male dominated in clonal seed plants and female dominated in clonal bryophytes. [source]


Inclusion of biotic stress (consumer pressure) alters predictions from the stress gradient hypothesis

JOURNAL OF ECOLOGY, Issue 6 2009
Christian Smit
Summary 1. ,The stress gradient hypothesis (SGH) predicts a shift from net negative interactions in benign environments towards net positive in harsh environments in ecological communities. While several studies found support for the SGH, others found evidence against it, leading to a debate on how nature and strength of species interactions change along stress gradients, and to calls for new empirical and theoretical work. 2. ,In the latest attempt in this journal, it is successfully argued how the SGH should be expanded by considering different life strategies of species (stress tolerance versus competitive ability) and characteristics of abiotic stress (resource versus non-resource based) over wider stress gradients (opposed to low,high contrasts), but the crucial role of biotic stress by consumers is largely ignored in this refinement. 3. ,We point out that consumers strongly alter the outcome of species interactions in benign and harsh environments, and show how inclusion of consumer-incurred biotic stress alters the predicted outcome of interactions along resource- and non-resource-based stress gradients for stress-tolerant and competitive benefactors and beneficiaries. 4. ,Synthesis. New studies should include stress gradients consisting of both abiotic and biotic components to disentangle their impacts, and to improve our understanding of how species interactions change along environmental gradients. [source]


Accuracy of prediction of walking for young stroke patients by use of the FIM

PHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 1 2001
Heather Thornton Senior Lecturer
Abstract Background and Purpose Clinical prediction of walking outcome after a stroke is essential for effective discharge planning. However, its accuracy has hardly been explored. This study took place in a regional unit admitting patients with complex neurological disabilities for specialist inpatient rehabilitation. The aim was to compare predicted outcome (goal score) with achieved outcome (discharge score) on the seven-point locomotion subscale of the Functional Independence Measure (FIM), to evaluate its precision and identify factors influencing accuracy. Method Admission, goal and discharge scores were analysed retrospectively for 141 subjects (90 M; 51 F) admitted consecutively to the Unit with median age 54 years (range 15,68 years) with median length of stay 13.6 weeks (range 3,35 weeks). Results Ninety subjects (64%) gained from two to six points; 50 subjects (35%) gained one point or showed no change. One patient deteriorated by two points. Excluding patients admitted with the highest score (FIM level 7), the overall level of agreement between predicted and discharge scores was moderate (weighted kappa 0.47). Prediction was accurate to ±1 point in 113 subjects (80%). Overprediction by ,2 points occurred in 16 subjects (11%) and underprediction by ,2 points in 12 subjects (9%). Analysis of the most-disabled cohort, admitted with FIM levels 1 or 2 scores, revealed a higher sensitivity for predicting ,independence' (FIM levels 5,7) (78%) than ,dependence' (FIM levels 1,4) (65%). Accuracy was not affected by age, gender or side of stroke. Inaccurate predictions were associated with lower admission FIM level scores (p=,0.26;p=0.002) and a greater length of stay (p=0.36;p<0.001). Subjects with quad-riplegia were more likely to have inaccurate outcome predictions made than those with hemiplegia (p=0.025) and those with neglect were more likely to have inaccurate outcome predictions made than those without neglect (p=0.017). Conclusion Further investigation into clinical prediction and the variables which confound accuracy is needed for effective planning. Copyright © 2001 Whurr Publishers Ltd. [source]


MEIOTIC DRIVE AND SEX CHROMOSOME CYCLING

EVOLUTION, Issue 5 2004
David W. Hall
Abstract , Sex-linked meiotic drive is found in a broad variety of taxa, including insects, birds, and mammals. In populations of some species, we see four types of sex chromosomes segregating: normal and driving X chromosomes and susceptible and resistant Y chromosomes. A theoretical analysis shows that a stable four-chromosome equilibria is a more common outcome in these systems than previously recognized. Cycling of sex chromosome frequencies and associated changes in the sex ratio are other predicted outcomes. The absence of cycling in nature may be due to migration among populations. [source]


Detrusor instability with equivocal obstruction: A predictor of unfavorable symptomatic outcomes after transurethral prostatectomy

NEUROUROLOGY AND URODYNAMICS, Issue 5 2002
Rintaro Machino
Abstract Aims To elucidate whether preoperative urodynamic findings can predict outcomes of transurethral resection of the prostate (TUR-P). Methods Sixty-two patients with symptomatic benign prostatic hyperplasia were categorized in three different ways based on findings of preoperative pressure-flow study (PFS) and cystometry: urodynamic obstruction (determined by the Abrams-Griffiths nomogram), detrusor instability (DI), and combination of both. Outcomes of TUR-P regarding symptom, function, and quality of life (QOL) were analyzed by changes in the International Prostate Symptom Score (I-PSS), maximum flow rate in uroflowmetry, and QOL index before and after TUR-P, respectively. Overall outcome was defined as success when all of the three categories showed successful improvement. Results Neither urodynamic obstruction alone nor DI alone predicted outcomes of TUR-P. However, symptomatic and overall outcomes were significantly worse in patients who were not obstructed but had DI. Postoperative persistent DI was more frequently noted in patients without clear obstruction (60%) than in those with obstruction (27%). Patients with equivocal obstruction showed less satisfactory symptomatic outcomes of TUR-P when DI was accompanied. Persistent DI might be the principle cause of unfavorable outcomes. Conclusions Preoperative evaluation of DI is of benefit because it enhances predictive value of the PFS. Neurourol. Urodynam. 21:444,449, 2002. © Wiley-Liss, Inc. [source]