Eficiencia en el uso de trampas de caída y suficiencia taxonómica en comunidades de arañas (Araneae) epigeas en tres ecorregiones del Noroeste Argentino

The increased degradation of natural habitats has strengthened the need to know and assess biodiversity patterns. Particularly, the study of the araneofauna in the North of Argentina is scarce in ecoregions with priority interests of conservation. Generally, spiders are used as indicators to compare biodiversity patterns, and here we tested whether the spider family-level can act as a substitute of the species-level in biodiversity rapid assessments. For this, we analyzed the alpha and beta diversity of the epigeal spider communities in three separate sites of different ecoregions of Salta province (Chaco Serrano, Monte de Sierras and Bolsones, and Puna), during the fall, winter, spring and summer of 2005 -2007. In each site, 10 pitfall traps, located along a linear transect and 10 meters apart, were placed for seven days per season of continuous activity. Samples were obtained, taken to the laboratory and identified. A total of 886 spiders were collected from 100 species/morphospecies of 19 families. The completeness of the inventory obtained for each ecoregion surpassed 70 %. The Chaco ecoregion (S = 56, N = 495) reported the highest species richness and abundance compared to Monte (S = 44, N = 262) and Puna (S = 23, N = 129). Alpha and beta diversity showed that ecoregional spider communities were different, sharing between them very few species (0.7 %). The Chaco reported a high dissimilarity of its assemblage with respect to the other ecoregions. The colder seasons (autumn and winter) proved to be important in assessing the diversity of spiders in these ecoregions, contributing to regional diversity in conjunction with the diversity of warm seasons (spring and summer). Four guilds were reported (ground hunters, specialists, other hunters and ambush hunters), but the latter was absent in Monte, and the specialists dominated in Chaco. Zodariidae was dominant in Chaco Serrano, where Leprolochus birabeni is an indicator of native environments. On the other hand, Lycosidae, Philodromidae, Anyphaenidae and Oonopidae were important for Monte and Puna. This way, the use of pitfall traps in all seasons of the year, and the recognition of spider families for epigeal fauna, was very useful for biodiversity rapid assessments in this area. Like the species-level, the taxonomic family-level evidenced changes in alpha and beta diversity. This allowed the inclusion of this taxonomic group for future biodiversity monitoring studies for conservation plans in these ecoregions.