Variation in Akodon cursor (Winge, 1887) (SIGMODONTINAE) Follows Bergamnn´s Rule

KAUFMANN CARLA, BIDAU CLAUDIO J., MARTÍ DARDO A. & GEISE LENA

Villa Giardino, Córdoba

Jornada; XXII Jornadas Argentinas de Mastozoología; 2008

SAREM

Akodon cursor, a medium-sized sigmodontine (adult body mass up to 40-45 g), ranges from southeastern and central Brazil through Uruguay, Paraguay, and northeastern Argentina. We studied body size variation in 70 Brazilian populations spanning 18.5 degrees latitude (6.83º-25.33º S), 14.23 longitude (34.57º-48.80º W) and 1170 metres (1-1170 m altitude), with relation to environmental factors in order to test Bergmann’s rule within this species. Estimators of body size independently calculated for males and females were, Head and Body Length (mm) and Body Mass (g) both transformed to decimal logarithms for analyses. Geographic body size variation was analyzed with SAM (Spatial Analysis in Macroecology v. 3.0; Rangel et al. 2006. Global Ecology and Biogeography 15: 321-327) software. Relative age was estimated by tooth wear. Independent variables included mean, maximum and minimum temperature, annual, maximum and minimum rainfall, the coefficients of variation of temperature and precipitation, actual and potential evapotranspiration, and water balance, calculated for each locality. In view of colinearity of many of the climatic variables, PCAs were performed and the first three or four PCs (delimited by the broken stick method) were used as independent variables for simultaneous autoregression analyses (SAR). PCs not significantly correlated with body size estimators, were discarded and climatic parameters with high loadings on the remaining PCs were used as single or combined independent variables in further SARs. The Akaike Information Criterion (AIC) was used to determine the best predictive model for body size geographic variation. In both females and males, mean annual temperature was highly negatively correlated with body size indicating that, A. cursor follows Bergmann’s rule. This results also concord with the fact that the genus Akodon, as a whole, also agrees with Bergmann’s rule at the across-species level (Bidau 2008. IV Congresso Brasileiro de Mastozoologia).