RESUMO
Population genetics theory predicts loss in genetic variability because of drift and inbreeding in isolated plant populations; however, it has been argued that long-distance pollination and seed dispersal may be able to maintain gene flow, even in highly fragmented landscapes. We tested how historical effective population size, historical migration and contemporary landscape structure, such as forest cover, patch isolation and matrix resistance, affect genetic variability and differentiation of seedlings in a tropical palm (Euterpe edulis) in a human-modified rainforest. We sampled 16 sites within five landscapes in the Brazilian Atlantic forest and assessed genetic variability and differentiation using eight microsatellite loci. Using a model selection approach, none of the covariates explained the variation observed in inbreeding coefficients among populations. The variation in genetic diversity among sites was best explained by historical effective population size. Allelic richness was best explained by historical effective population size and matrix resistance, whereas genetic differentiation was explained by matrix resistance. Coalescence analysis revealed high historical migration between sites within landscapes and constant historical population sizes, showing that the genetic differentiation is most likely due to recent changes caused by habitat loss and fragmentation. Overall, recent landscape changes have a greater influence on among-population genetic variation than historical gene flow process. As immediate restoration actions in landscapes with low forest amount, the development of more permeable matrices to allow the movement of pollinators and seed dispersers may be an effective strategy to maintain microevolutionary processes.
Assuntos
Euterpe/genética , Variação Genética , Genética Populacional , Brasil , Ecossistema , Fluxo Gênico , Deriva Genética , Endogamia , Repetições de Microssatélites , Modelos Genéticos , Densidade Demográfica , Árvores/genéticaRESUMO
PURPOSE: To evaluate the quality of reporting of all the new randomized clinical trials published during 1999 in OPHTHALMOLOGY: using the CONSORT statement parameters. DESIGN: Descriptive series of published studies. STUDIES INCLUDED: Randomized clinical trials. METHODS: Eligible studies were all randomized clinical trials published in Volume 106 (1999) of OPHTHALMOLOGY: that reported the results of prospectively conducted studies in humans comparing two or more therapeutic options with regard to their effect on one or various outcomes, in which the authors stated that a process of randomization or quasi-randomization was performed before the interventions. Each study was evaluated by two independent observers establishing the specific report in the published manuscript of 57 CONSORT statement descriptors, and consensus was obtained between evaluators. MAIN OUTCOME MEASURES: Overall presence of CONSORT statement descriptors in published reports. RESULTS: The mean number of positive CONSORT descriptors for the 24 eligible randomized clinical trials was 33.42 (standard error of the mean [SEM] 1.57) of 57 possible. This score was significantly different (P: < 0.001) from the score of 16.6 (standard error of the mean 0.6) reported for OPHTHALMOLOGY: in the 1991 to 1994 study by Scherer and Crawley. Of the nine descriptors measuring the quality of abstract reporting, a mean of 6.25 (SEM 0.3) was included in the 24 study abstracts evaluated, significantly different from the Scherer and Crawley score (5.2, SEM 0.2. P: < 0.001). Four and six descriptors increased and decreased, respectively, their reporting in more than 20%. Key descriptors such as hypothesis postulation, primary outcome determination, sample size calculations, and a discussion of the limitations of the study such as bias, imprecision, and internal validity are still reported in less than 42% of clinical trials. CONCLUSIONS: This study describes for the first time after the adoption of the CONSORT statement recommendations the status on the quality of reporting of recently published randomized clinical trials in OPHTHALMOLOGY: Although not a direct measure of the intrinsic quality of a study, reporting quality provides the reader with useful tools for the evaluation of its validity. The quality of reporting of randomized clinical trials shows an overall improvement when compared with the period between 1991 and 1994. However, there is still significant room for improvement, especially in descriptors essential for the validation of clinical trial results that are still widely underreported.
Assuntos
Oftalmologia/normas , Editoração/normas , Ensaios Clínicos Controlados Aleatórios como Assunto/normas , Guias como Assunto/normas , Humanos , Estudos Multicêntricos como Assunto/normas , Controle de Qualidade , Projetos de PesquisaRESUMO
Electrophoretic variants for seven isozyme systems - probably encoded by 18 structural gene loci - in diploid populations of Larrea divaricata and diploid and tetraploid populations of its North American vicariant derivative L. tridentata were assayed by polyacrilamide and starch gel electrophoresis. High molecular similarity of diploid and tetraploid cytotypes of L. tridentata supports the hypothesis of interracial autopolyploidy. The absence of fixed heterozygosity and additive profiles indicates a low level of divergence between the parental diploids and the tetraploids. The phenogram based on the I coefficient showed the similarities between the populations of diploid L. divaricata and also between the diploid populations of L. tridentata. Both groups of diploid populations were more distantly connected to tetraploid L. tridentata.
RESUMO
A ten year old girl with Saethre-Chozen's syndrome and normal intelligence is described and her phenotype is compared to previously reported cases.