No abstract

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.

Factors influencing the diversity of tenebrionid beetles in arid, high-altitude environments in the northwest of Argentina are little-known. Using pitfall traps and suction sampling in 30 sites, we collected these beetles in Altos Andes (AA) and Puna (PU) ecoregions and evaluated how local and regional factors influenced their assemblages. During each sampling date, we registered variables related to climate, vegetation, and soil in each sampling site. In total, we recorded 270 individuals from 21 species, richness of species was higher in PU than in AA, but without a statistically significant difference. Twelve species were present exclusively in PU, while two in AA.Tenebrionid assemblages in both ecoregions had different dominant species, in PU, Psectrascelis cariosicollis while Epipedonota interandina in AA. Beta diversity between ecoregions was moderate and we recorded a high beta diversity and high turnover of species in each ecoregion. The geographical distance between the sites influenced the similarity of the assemblages inside and between ecoregions, therefore, an increase in the geographical distance between sites determined a decrease in the similarity of the assemblages. The increase in elevation of the sampled sites did not produce significant changes in the abundance and richness of Tenebrionidae. There is no individual factor responsible for the darkling beetle communities structuration in these high-altitude environments. Different combinations of both local (soil and vegetation) and regional (climate and geographical distance) environmental factors together explain the ecoregional tenebrionid assemblages. We suggest including them among the focus groups in conservation studies to evaluate anthropogenic activities in this area.