Distributional patterns of small mammals along elevational gradients in northwestern Argentina

Abstract

We describe the altitudinal variation in species richness, turnover and species composition of small mammalsthrough field surveys along 4 transects ranging from tropical rainforests at 500 m to high Andean deserts at 4 000 m innorthwestern Argentina. The elevation pattern of richness for all small mammals decreases with altitude, mainly dueto the high diversity of bats in the lowlands. For the terrestrial small mammals there was a clear curvilinear patternof richness with a peak near the upper tree line at 2 700 m. The maximum values of the species turnover rates werelocated in the upper part of the gradient at 3 500 m. The composition of small mammals communities in every singleelevation transect was consistent with the phytogeographic scheme, with species characteristics of montane rainforest,temperate cloud forests and high Andean steppes. The analysis of the 4 altitudinal transects together revealed thatelevation is the main source of variation in species composition. Latitudinally, the 2 northernmost transects, similarbetween each other, differed from the 2 southernmost, mainly at intermediate elevation, where a high concentrationof endemic rodents has been documented.