RICHNESS OF SMALL MAMMALS IN THE CENTRAL ANDES OF ARGENTINA: ENVIRONMENTAL AND

NOVILLO, AGUSTINA & OJEDA, RICARDO A.

Mendoza, Argentina

Congreso; Xth International Mammalogical Congress; 2009

Internationational Federation of Mammalogists

Interest in species richness patterns along altitudinal gradients has increased in the last decade. Among predominant patterns we can mention: a monotonic decrease in richness with increasing elevation and a hump-shaped pattern where richness peaks at an intermediate elevation. Several hypotheses about which environmental factors are responsible for species richness have also been made, for example: richness will decrease with a diminishing temperature and will increase with an increment in precipitation or show a hump shape pattern (as in most arid mountains). Other factors that can influence altitudinal richness gradients are geographic constraints (mid-domain null models) and historical evolution of lineages in the area. We examine the shape of Andean small mammal’s altitudinal gradient and the role of climatic parameters in determining this gradient. Four altitudinal transects (from 32° S to 35°S) were sampled (from 1300 m to 3300 m, at an interval of 500 m); 150 Sherman like traps were set at each site, during 3 consecutive nights. Climate data included 4 variables (Annual Mean Temperature, Temperature seasonality, Annual Precipitation, Precipitation seasonality) obtained from WorldClim database. Mid domain null models were performed using Range Model. To assess the best model which explains richness altitudinal gradients we performed generalized linear model (GLM). Models were selected according Akaike information criteria. Our results show that environmental variables (temperature and precipitation) explain more than 85% of species richness along elevation gradients. Furthermore, richness shows a negative relationship with temperature (R: 0.3546, p: 0.005603) and a positive relationship with precipitation (R: 0.5858, p: 8.417e-05). On other hand our data suggests that geographic constraints do not play a major role in structuring small mammal assemblages along the Andes. The inverse relationship of richness along elevation supports the long history of the sigmodontine rodents in the Andes.