Predators can exert strong direct and indirect effects on ecological communities by intimidating their prey. The nature of predation risk effects is often context dependent, but in some ecosystems these contingencies are often overlooked. Risk effects are often not uniform across landscapes or among species. Indeed, they can vary widely across gradients of habitat complexity and with different prey escape tactics. These context dependencies may be especially important for ecosystems such as coral reefs that vary widely in habitat complexity and have species-rich predator and prey communities. With field experiments using predator decoys of the black grouper (Mycteroperca bonaci), we investigated how reef complexity interacts with predation risk to affect the foraging behaviour and herbivory rates of large herbivorous fishes (e.g. parrotfishes and surgeonfishes) across four coral reefs in the Florida Keys (USA). In both high and low complexity areas of the reef, we measured how herbivory changed with increasing distance from the predator decoy to examine how herbivorous fishes reconcile the conflicting demands of avoiding predation vs. foraging within a reefscape context. We show that with increasing risk, herbivorous fishes consumed dramatically less food (ca. 90%) but fed at a faster rate when they did feed (ca. 26%). Furthermore, we show that fishes foraging closest to the predator decoy were 40% smaller than those that foraged at further distances. Thus, smaller individuals showed muted response to predation risk compared to their larger counterparts, potentially due to their decreased risk to predation or lower reproductive value (i.e. the asset protection principle). Habitat heterogeneity mediated risk effects differently for different species of herbivores, with predation risk more strongly suppressing herbivore feeding in more complex areas and for individuals at higher risk of predation. Predators appear to create a reefscape of fear that changes the size structure of herbivores towards smaller individuals, increases individual feeding rates, but suppresses overall amounts of primary producers consumed, potentially altering patterns of herbivory, an ecosystem process critical for healthy coral reefs.

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El presente artículo tiene como objetivo describir las transformaciones de prácticas pedagógicas y uso pedagógico de la argumentación en docentes, a partir del apoyo de materiales curriculares soportados tecnológicamente con un software piloto denominado argumentApp. Se utilizó una metodología cualitativa, mediante el estudio de cuatro casos de profesores y estudiantes de cuatro escuelas de la Región Metropolitana en Chile. Los datos, recogidos mediante observaciones de clases y entrevistas en profundidad, indican que los docentes incorporaron prácticas colaborativas en el aula y produjeron un mayor número de preguntas de argumentación. Se observan diferencias en el modo de apropiarse de la herramienta tecnológica y de su aporte a la dinámica de aprendizaje en el aula. Los resultados se discuten considerando el aporte de intervenciones de desarrollo profesional situadas en un contexto concreto de práctica y las dimensiones que permiten construir una intervención que favorezca una enseñanza dialógica.