Biodiversity of arthropods and terrestrial vertebrates of the Chile's Norte Grande

To assess the terrestrial arthropod and vertebrates diversity of arid II Re gion of Chile from early Winter 1996 to late Fall 1998, the animal biodiver sity of 23 sites located within 21 and 25 degrees S of Chile's Big North, a nd ranging in elevation from sea level to above 4 000 m, was surveyed. Site s covered coastal desert, continental desert, pre-Andean tropical and Andea n tropical di Castri's bioclimatic zones. At these sites the taxonomic or p hyletic diversity for vascular plants and its associated arthropods, as wel l as alpha, beta and gamma diversities for reptiles, terrestrial birds and small mammals were calculated. Over all sites, we found 97 plant species an d 464 morphospecies of associated arthropods. Arthropod diversity and the p resence of galls were related to functional plant characteristics such as w ater and nitrogen content. Phytophagous gall-making insects increased with altitude. Among vertebrates, we found nine reptile, 80 bird and IS small ma mmal species. Most reptile species were present either at low or high eleva tion. These were often unique sites. Reptiles showed low alfa and gamma, an d high beta diversities. Bird species richness, diversity, and abundance we re not associated with an elevational gradient made up of nine sites. Howev er, for birds, compared to gamma diversity, some low-elevation sites had hi gh alpha diversities. Bird gamma diversity was higher than maximum values r eported elsewhere. Bird beta diversities were intermediate or high, owing t o several species found only at one site, which was supported by low simila rities among sites. Some sites had high raptor species richness. The small mammals had low alpha and intermediate gamma diversities values, but had th e highest beta diversity found in this study. Small mammals alpha diversiti es were similar at low and high-altitude sites. The occurrence of an ENSO e vent starting during the Winter of 1997, allowed us to assess a quick respo nse of the granivore species bird, Phrygilus fruticeti. In contrast, small mammals responded with a time delay, which was significant for the sigmodon tine rodent Abrothrix andinus.