Egeria densa Planchon is considered an invasive species in continental aquatic systems in Chile. Its original geographical distribution was limited to the subtropical regions of Brazil, Argentina and Uruguay. Its fast growth and dense canopy-forming habit are associated with the clear water state of shallow water continental ecosystems. As a dominant species in many of the systems in which it occurs, E. densa behaves as an ecosystem engineer by preventing the re-suspension of sediments and controlling the growth of phytoplankton by removing nutrients from the water column. At the same time, this invasive species produces unwanted effects such as: (1) clogging waterways and hydroelectric turbines, (2) out-competing native vegetation, and (3) negatively affecting the sediment seed bank. Given its importance in the recent (2004) change of state of the Río Cruces wetland, Chile, we felt it appropriate to undertake a comprehensive literature review of this species. We conclude by discussing the role of E. densa as an ecosystem engineer while cautioning against the impression that E. densa is always a highly competitive invader.Key words: Egeria densa, ecosystem engineer, invasive species. RESUMENEgeria densa Planchon es considerada una especie invasora en los sistemas acuáticos de Chile. Su distribución geográfica original estaba limitada a regiones subtropicales de Brasil, Argentina y Uruguay. Su crecimiento rápido y su tendencia a formar densas coberturas suelen estar asociadas con el estado de aguas claras en ecosistemas acuáticos continentales de aguas someras. Su dominancia sugiere que E. densa puede comportarse como una especie ingeniera, previniendo la resuspensión de sedimentos y controlando el crecimiento del fitoplancton a través de la utilización de los nutrientes. Sin embargo, al mismo tiempo, como especie invasora produce efectos no deseados tales como: (1) no permitir el crecimiento de otras macrófitas nativas, (2) disminuir la diversidad en el banco de semillas, y (3) interferir con la navegación y generación de electricidad por turbina. Dada su importancia en el reciente (2004) cambio de estado del humedal del Río Cruces, nos ha parecido oportuno realizar una recopilación de artículos científicos disponibles en la literatura sobre esta macrófita. Concluimos con una discusión sobre el rol de E. densa como especie ingeniera; a la vez que indicamos que la especie tiene ciertas vulnerabilidades y que no cumple siempre con la idea que es una especie invasora muy competitiva.Palabras clave: Egeria densa, especie ingeniera, especie invasora.

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Identifying which ecosystem services are relevant to different stakeholders and understanding stakeholders’ perceptions of such services is useful for making informed decisions, especially in regions of the world where the achievement of biodiversity conservation goals is threatened by economically productive activities. In this article, we assess social preferences for ecosystem services in a biodiversity hotspot in central Chile. We use a consultative case study to ask local stakeholders (n = 70) from the Campana Peñuelas Biosphere Reserve to identify the most important ecosystem services the area provides for them and inquire about the perceived vulnerability of the services to changes in the future. We also explore the association between the perceived importance of ecosystem services and the sociodemographic and cultural characteristics of the respondents, which allows us to identify contrasting stakeholder perceptions of different ecosystem services. The most important services for local actors were the drinking water, fresh air and climate change control, genetic pool of plant communities in central Chile, and educational value. From the perspective of local actors, the services that could be threatened by negative changes in the future in terms of their provision included the possibilities of developing conservation activities focused on iconic threatened animal and plant species, water regulation, food from agriculture, and drinking water. Contrasting perceptions about the importance of ecosystem services emerged among stakeholders. While small farmers and members of local organizations attributed higher importance values to provisioning services, scientists and rangers and administrators of protected areas as well as teachers, NGO members and local government employees attributed more importance to the regulating and cultural services associated with threatened species. Our results can serve as a source of information for the planning and decision-making processes related to the search for socially and ecologically sustainable solutions for land use management.