It is an important input for conservation of biodiversity to survey the presence of exotic species and to know their environmental attributes. Through literature reviews and scientific collections, we were able to collect data on diet, body size, history and status of invasion of exotic mammals reported in Uruguay. Niche modeling was conducted for each species based on Maximum Entropy models. Also we estimated the changes generated in the trophic structure of the biota of the mammals in Uruguay caused by the processes of species introductions and losses. Changes in mammal's body size were evaluated in relation to the size distribution data for the main estimated trophic groups. This analysis was performed at the species richness level, and the total biomass per trophic group was estimated considering the known allometric relationships. Our results suggest that the change in biomass can be estimated only by knowing the allometric exponent between density and body size, without knowing the normalization constant. The recently extinct species were of greater body size and more carnivorous diets, often compared to the current ones. In contrast, introduced species are omnivorous (Mus musculus, Rattus norvegicus, Rattus rattus, Sus scrofa) and herbivorous (Lepus europaeus, Bubalus bubalis, Capra hircus, Axis axis, Dama dama). Considering trophic level biomass, these changes in species composition are exacerbated. In addition, we evaluate the climatic suitability of the Uruguayan territory for the establishment of two potentially invasive species, the red-bellied squirrel (Callosciurus erythraeus), which is expanding its range in Argentina, and the American mink (Neovison vison) which has been recently introduced in Uruguay for commercial breeding purposes. Despite the relative landscape geographical and climate homogeneity in Uruguay, our estimates for environmental suitability of the potential establishment of exotic species indicate significant changes over the territory and between species. Our study highlights the strength of ecological theory to advance in the basic status of the species, and their impact, even when information on these and the invasion sites are limited.

Relevar la presencia de especies exóticas y conocer sus atributos ecológicos es un importante insumo para la conservación de la biodiversidad. A través de una revisión bibliográfica y de colecciones científicas, se recabaron datos de dieta, tamaño corporal, historia y estatus de invasión de los mamíferos exóticos reportados en Uruguay. Se realizaron modelaciones de nicho para cada especie en base a modelos de Máxima Entropía. También se estimó el cambio generado en la estructura trófica de la biota de mamíferos del Uruguay causado por los procesos de introducción y pérdida de especies. El cambio en los tamaños corporales se evaluó en relación a los datos de distribución de tamaños estimados para los principales grupos tróficos de mamíferos. Este análisis se realizó a nivel de riqueza de especies y biomasa total por grupo trófico, estimada a partir de alometrías conocidas. Los resultados sugieren que el cambio en biomasa es estimable sólo conociendo el exponente de las alometrías entre densidad y tamaño corporal, no requiriéndose conocer la constante de normalización. Las especies recientemente extintas son de mayores tamaños corporales y frecuentemente de dietas carnívoras en comparación a las actuales. Contrariamente, las especies introducidas son omnívoras (Mus musculus, Rattus norvegicus, Rattus rattus, Sus scrofa) y herbívoras (Lepus europaeus, Bubalus bubalis, Capra hircus, Axis axis, Dama dama). Estos cambios en la composición de especies se ven exacerbados cuando los consideramos desde el punto de vista de la biomasa. Asimismo evaluamos la idoneidad climática del territorio uruguayo para el establecimiento de dos especies potencialmente invasoras, la ardilla de vientre rojo (Callosciurus erythraeus) que estaría expandiendo su rango de distribución en Argentina y el visón americano (Neovison vison) que ha sido recientemente introducido con fines de cría comercial. No obstante la relativa homogeneidad geográfica y climática del paisaje de Uruguay, las estimaciones de idoneidad ambiental para el potencial de establecimiento de especies exóticas indican importantes variaciones a lo largo del territorio y entre especies. Nuestro estudio remarca la fortaleza de la teoría ecológica para adelantarse en el estado básico de las especies y su impacto, incluso cuando la información disponible sobre éstas y los sitios de invasión es limitada.

Scinax aromothyella is a recently described hylid frog. Its distribution is not well known. There are records for Misiones, Argentina and for southeastern Uruguay. Here we report a new record of S. aromothyella from Aceguá, Cerro Largo Department, Uruguay (31° 53' 39" S and 54° 9' 17" W), based in tadpoles collected on the 15 of August, 2007. This new record extends the distribution of S. aromothyella in approximately 100 km north from previous reports in Uruguay. The samples were collected in a site located 2 km away from the border line with Brazil, reinforcing the idea that S. aromothyella might occur in Rio Grande do Sul.

Scinax aromothyella es un anfibio hilido recientemente descripto y con distribución poco conocida. Existen registros de Misiones, Argentina, y del sureste de Uruguay. Reportamos en este trabajo un nuevo registro de S. aromothyella para el Departamento de Cerro Largo, Uruguay, localidad Aceguá (31° 53' 39" S y 54° 9' 17" W) basado en renacuajos colectados el 15 de agosto de 2007. Este registro extiende la distribución de S. aromothyella más de 100 km al norte de los registros previos en Uruguay. La cercanía a la frontera (2 km) refuerza la idea de la ocurrencia de esta especie en el sur de Brasil.

Nós examinamos a dieta de 4 peixes anuais, Austrolebias viarius, Austrolebias cheradophilus, Austrolebias luteoflammulatus e Cynopoecilus melanotaenia, que habitam poças temporárias do sudeste do Uruguai, através da análise de conteúdo estomacal. Os peixes foram capturados em cinco poças temporárias da bacia da lagoa Castillos, na região de Humedales del Este. Nós identificamos 13099 itens de presas estraídos de 669 estômagos das quatro espécies. No sistema estudado, peixes anuais representam os predadores de topo mais abundantes e conspícuos. Os rivulídeos são predadores generalistas nas poças temporaries estudadas, consumindo principalmente itens aquáticos. Zooplâncton representou o item principal da dieta para as quatro espécies, seguido de ovos, algas e diatomáceas. Insetos compoem o próximo grupo em número de presas, como segue: larvas de Diptera (especialmente Chironomidae e Cullicidae), Ephemeroptera (especialmente Betidae), e larvas de Coleoptera (especialmente Dytiscidae). Ácaros foram também presas importantes em número. As quatro espécies de peixes diferem na composição e riqueza das dietas. O padrão geral de diferenciação da dieta entre espécies e grupos demográficos de rivulídeos pode ser relacionado à variação do tamanho corporal. Como predadores de topo, os rivulídeos anuais são um componente importante dos ecossistemas de poças temporárias. A compreensão da história natural destas espécies e de suas comunidades é necessária a sua conservação.

We examined the diet of 4 annual fishes, Austrolebias viarius, Austrolebias cheradophilus, Austrolebias luteoflammulatus and Cynopoecilus melanotaenia inhabiting temporal ponds of southeastern Uruguay, by analysis of stomach contents. Fishes were captured from fifty ephemeral ponds of Castillos Lagoon basin, in the region of the Humedales del Este. We identified 13099 individual prey items extracted from 669 stomachs of the four captured species. In the studied system, annual killifishes represents the most abundant and conspicuous top predators. Killifishes are generalist key predators at the ephemeral ponds of the studied system, consuming mostly aquatic items. Zooplancton represented the bulk of the diet in the four analyzed species, followed by eggs, algae and diatoms. Insects are the next group in prey number, as follows: Diptera larvae (especially Chironomidae and Cullicidae), Ephemeroptera (especially Betidae), and coleopteran larvae (especially Dytiscidae). Acari are also important prey in number. The four fish species differ in diet composition and in diet richness. A general pattern of differences in diet richness among killifish species and demographic groups could be related to variations in body sizes. As top predators annual killifishes are an important component of the temporal pond ecosystems. Understanding the natural history of this species and their communities is necessary in order to conserve them.