El ensamble de arañas en un hotspot dendroflorístico del este de Uruguay

In previous studies, Uruguay has been considereda biogeographical crossroads. Paso Centurión and Sierra de Ríos in eastern Uruguay were recently enteredi nto the National System of Protected Areas. Thelandscape is characterized by a mosaic of differentecosystems located in one of the dendrofloristic hotspots proposed for the country. The spiders constitute a megadiverse group useful for the monitoring of natural environments. The aim of this study was toknow the composition and structure of the spider faunaof this protected area. The sampling of spiders was carried out in two different environments (ravine andriparian forests) and three methods were used: groundvacuum, foliage beating and manual collection. Agreater richness of spider families, species and guilds was recorded compared to previous studies in other protected areas from Uruguay. The two environments showed differences in taxonomic composition and species replacement. Araneidae, Theridiidae and Salticidae represented the families with the high estspecies richness. The family Symphytognathidae and55 species are new records for the country. The finding of more southern records for several species confirm that the area is located in a border zone with other biogeographic units at regional level. This fact supports the crossroads condition for the country, provides key information for the management of the area and increases the number of priority spider species for conservation in UruguayEstudios recientes han considerado a Uruguay como una encrucijada biogeográfica. Paso Centurión y Sierra de Ríos en el este de Uruguay fue recientemente ingresado al Sistema Nacional de Áreas Protegidas. El paisaje está caracterizado por un mosaico de diferentes ecosistemas situado en uno de los hotspots dendroflorísticos propuestos para el país. Las arañas constituyen un grupo megadiverso que es útil para el control de los entornos naturales. El objetivo del estudio consistió en conocer la composición y estructura de la araneofauna de esta área protegida. El estudio se llevó a cabo en dos tipos de ambientes (bosque ribereño y bosque de quebrada) y se utilizaron tres métodos: aspirador de suelo, batido de follaje y recolección manual. Se registró una mayor riqueza de familias, especies y gremios de arañas en comparación con estudios previos en otras áreas protegidas de Uruguay. Los dos ambientes mostraron diferencias en la composición taxonómica y reemplazo de especies. Araneidae, Theridiidae y Salticidae fueron las familias con mayor riqueza específica. La familia Symphytognathidae y 55 especies son nuevos registros para el país. El hallazgo de registros más australes para varias especies confirma que esta área se encuentra en una zona límite con otras unidades biogeográficas a nivel regional. Esto refuerza el carácter de enclave biogeográfico para el país, aporta información relevante para el manejo del área y aumenta el número de especies prioritarias de arañas para la conservación en Uruguay

Spider assemblages associated with different crop stages of irrigated rice agroecosystems from eastern Uruguay

The rice crop and associated ecosystems constitute a rich mosaic of habitats that preserve a rich biological diversity. Spiders are an abundant and successful group of natural predators that are considered efficient in the biocontrol of the major insect pests in agroecosystems. Spider diversity in different stages of the rice crop growth from eastern Uruguay was analysed. Field study was developed on six rice farms with rotation system with pasture, installed during intercropping stage as cover crop. Six rice crops distributed in three locations were sampled with pitfall and entomological vaccum suction machine. Sixteen families, representing six guilds, were collected. Lycosidae, Linyphiidae, Anyphaenidae and Tetragnathidae were the most abundant families (26%, 25%, 20% and 12%, respectively) and comprised more than 80% of total abundance. Other hunters (29%), sheet web weavers (25%) and ground hunters (24%) were the most abundant guilds. Species composition along different crop stages was significantly different according to the ANOSIM test. The results showed higher spider abundance and diversity along the crop and intercrop stages. This study represents the first contribution to the knowledge of spider diversity associated with rice agroecosystem in the country