The hypothesis that biotic interactions strengthen toward lower latitudes provides a framework for linking community-scale processes with the macroecological scales that define our biosphere. Despite the importance of this hypothesis for understanding community assembly and ecosystem functioning, the extent to which interaction strength varies across latitude and the effects of this variation on natural communities remain unresolved. Predation in particular is central to ecological and evolutionary dynamics across the globe, yet very few studies explore both community-scale causes and outcomes of predation across latitude. Here we expand beyond prior studies to examine two important components of predation strength: intensity of predation (including multiple dimensions of the predator guild) and impact on prey community biomass and structure, providing one of the most comprehensive examinations of predator-prey interactions across latitude. Using standardized experiments, we tested the hypothesis that predation intensity and impact on prey communities were stronger at lower latitudes. We further assessed prey recruitment to evaluate the potential for this process to mediate predation effects. We used sessile marine invertebrate communities and their fish predators in nearshore environments as a model system, with experiments conducted at 12 sites in four regions spanning the tropics to the subarctic. Our results show clear support for an increase in both predation intensity and impact at lower relative to higher latitudes. The predator guild was more diverse at low latitudes, with higher predation rates, longer interaction durations, and larger predator body sizes, suggesting stronger predation intensity in the tropics. Predation also reduced prey biomass and altered prey composition at low latitudes, with no effects at high latitudes. Although recruitment rates were up to three orders of magnitude higher in the tropics than the subarctic, prey replacement through this process was insufficient to dampen completely the strong impacts of predators in the tropics. Our study provides a novel perspective on the biotic interaction hypothesis, suggesting that multiple components of the predator community likely contribute to predation intensity at low latitudes, with important consequences for the structure of prey communities.
The intensity of biotic interactions is hypothesized to increase towards the equator. Predation can have a stronger effect on prey composition, biomass and taxonomic diversity in tropical regions compared to higher latitudes. Whether predation also shapes patterns of functional diversity and structure of prey communities, however, has rarely been explored across a latitudinal gradient. History of co‐occurrence between predators and prey may also shape the outcome of the interaction, and increased novelty of introduced prey may lead to stronger trait responses. We investigated the influence of predation on trait responses of prey communities across 12 sites in four regions, from the sub‐arctic to the tropics, using a field experiment in invaded coastal habitats. Prey communities experienced ambient or reduced predation pressure during assembly, and the effect of predation on functional diversity and structure of whole communities as well as their native and introduced components was assessed. Overall, predation increased functional diversity in the tropics, but effects were evident for introduced species only. Predation also shaped functional structure of low‐latitude communities, but effects were strongest for native species in subtropical Mexico and introduced species in tropical Panama. Key traits driving shifts in functional structure were related to palatability and reproduction. In the tropics, the strong predation present under ambient conditions reduced the abundance of palatable traits in introduced prey relative to low‐predation treatments, while in the subtropics, ambient predation increased the abundance of palatable traits in native prey. Reproductive traits that require high parental or energetic investment were favoured in low‐predation treatments at both low‐latitude regions. In summary, predation had a stronger influence on trait responses of prey communities at lower latitudes where biotic interactions are expected to be more intense, but changes in functional diversity and structure hinged on co‐occurrence histories of local predators with native or introduced prey. This study provides one of the first examinations of the effects of predation on functional trait responses of prey communities across a latitudinal gradient.
Arch Argent Pediatr 2011;109(6):492-498 / 492 RESUMEN Introducción. La observación directa de los alumnos por parte de distintos docentes en forma periódica, en diversos escenarios y en tiempo real, tiene gran valor en el proceso de formación. Objetivos. Evaluar la factibilidad en la implementación de una versión del Ejercicio de Examen Clínico Reducido adaptada a Pediatría, describir las evaluaciones realizadas según el ámbito de observación, la complejidad del paciente, el foco del encuentro y la situación pediátrica, y conocer la satisfacción de docentes y alumnos con respecto a esta herramienta. Método. Participaron en forma voluntaria todos los docentes y alumnos de la carrera. Las observaciones tenían carácter formativo. Las competencias evaluadas fueron: habilidades para la conducción de la entrevista, para el examen físico, para el asesoramiento, profesionalismo, criterio clínico, eficiencia y competencia clíni-ca global. Se definió la factibilidad del estudio como la posibilidad de realizar cuatro observaciones en al menos 70% de los participantes y que se llevaran a cabo observaciones en todas las áreas de rotación. Resultados. Se realizaron 388 observaciones. Participaron 54 alumnos y 50 docentes. Se realizaron 7,18 observaciones por participante, en el ámbito ambulatorio en el 57% y con baja complejidad en el 60% de los casos. El 85% de los participantes fueron observados mientras conducían una consulta de supervisión en salud. La calificación por competencia específica fue uniforme. El foco del encuentro presentó variaciones según el ámbito de observación. Docentes y alumnos se mostraron satisfechos. Conclusión. El instrumento pudo aplicarse con la frecuencia preestablecida, en los ámbitos programados y fue bien aceptado. Palabras clave: educación médica, posgrado, pediatría, competencias, observación directa, Mini-Cex. SUMMARY Aims.Faced with the increased challenge of assessing competences in young doctors, the purpose of the study was to evaluate the implementation of a pediatric version of the Mini-Cex in pediatric trainees as well as the level of satisfaction of teachers and students with the new assessment tool. Methods and results. From July 2007 to August2009, 54 pediatric trainees were periodically monitored in a variety of clinical settings by 50 teachers. The competences evaluated included medical interviewing, physical examination and counseling skills, humanistic qualities/ professionalism, clinical judgment, organization and overall clinical competence. The feasibility of this study was defined as an average 4 observations per participant, and observations in all clinical rotations. During the study, 388 observations were carried over 54 students (average of 7.18 observations per student); 57% took place in ambulatory settings, 60% were of low complexity and 85% involved healthy children programmed consultations. The ratings for specific competences had little variation; the focus related to the setting. Conclusions. Used in a variety of settings, with different patient problems, the m...
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