Abstract

RICO-CERNOHORSKA, Adriana et al. Altitudinal variation of species composition of small non-flying mammals in the Yungas region of Bolivia. Therya [online]. 2020, vol.11, n.3, pp.447-458.  Epub Apr 30, 2021. ISSN 2007-3364.  https://doi.org/10.12933/therya-20-1000.

The Cotapata National Park and Natural Area for Integrated Management (PN-ANMI) is located on the eastern escarpments of the Eastern Cordillera in Bolivia. It has an altitudinal range between 1,100 to 5,600 masl, with five altitudinally delimited ecological zones. There is great variability of environments, which generates great animal species diversity, varying according to elevation, and in association with changes in climatic and ecological conditions. The aim of this study was to determine the pattern of richness and composition of small non-flying mammals along an altitudinal gradient in the PN-ANMI Cotapata and to evaluate responses of these species to the gradient. We worked at three different elevations: Yungas Forest (1,400 masl), Cloud Forest (2,100 masl) and Yungas Paramo (3,500 masl). Six temporary replicas were conducted. For each sampling period we run three 250 m linear transects were placed, separated by 50 m attitudinally. Each transect contained 25 sampling stations, with two snap traps. With the exception of Yungas Paramo (due to the rocky ground), we also run transects of pitfall barrier traps (five buckets, every 5 m). We captured 460 specimens corresponding to 20 species of rodents and two of marsupials. Although, species richness (S) and diversity (Cinv) were higher in Cloud Forest (intermediate elevation; S = 11, Cinv = 4.30), followed by Yungas Forest (S = 9, Cinv = 3.47), and lower in Yungas Paramo (higher elevation; S = 8, Cinv = 2.12), only the diversity was significantly different (H = 7.0, n = 17, P = 0.03). Species composition varied between places, showing the greatest turnover between Cloud Forest and Yungas Paramo, with a similarity of only 2 %. Yungas Paramo had the highest number of exclusive species (seven of the eight registered). The diversity was higher at medium altitude, giving a positive monoclinal hump-shaped pattern. This variation, responds to climatic influences associated with changes in vegetation, where Cloud Forest provides a greater diversity of ecological niches. The lower diversity in Yungas Paramo, and the almost total species turnover responds to inhospitable and stress conditions and to the physiological adaptations of these species to these elevations.

Keywords : altitudinal gradient; Cotapata National Park; distribution; rodents; eastern mountain range; non-volant small mammals; replacement.