Differential effects of climate, environment, and land use on two sympatric species of Akodon

We describe changes in abundance of two rodent species over a 12-year period and assess the relationship between population abundance, climate, and agricultural practices in southern Cordoba Province, Argentina. We estimated abundance from trapping edges of agricultural areas, railway rights of way, and roadsides. Variables considered were: normalized difference vegetation index (NDVI), surface temperature, minimum and maximum temperature, rainfall, and cultivated areas of different crops. Species abundances varied over time; those of Akodon dolores declined, whereas those of A. azarae increased. Climatic and environmental changes may have had differential influences on species abundances. Autumn abundance of A. dolores was positively related to spring rainfall and area of harvested sorghum, and negatively related to NDVI. Akodon azarae abundance was negatively correlated with winter minimum temperature, spring rainfall, and sorghum harvested area, but positively associated with NDVI. On the other hand, both species were negatively correlated with each other. We suggest that environmental conditions may have changed the competition outcome for Akodon spp., and thus, had direct, differential effect on species abundances.