Intraspecific differences in metabolic rate of Chroeomys olivaceus (Rodentia : Muridae): the effect of thermal acclimation in arid and mesic habitats

Abstract

Studies of metabolic capacities in rodents have been largely Studied at an inter-specific levels, but physiological capacities of populations belonging to the same species have received lesser attention. Here we studied the maximum and basal metabolic rates Of two Populations of the rodent Chroeomys olivaceus dwelling in habitats with contrasting temperature and rainfall regimes, and to test if differences ill metabolic capacities are due to local adaptation or acclimatization effect. After four weeks of acclimation to 25 and 10 degrees C, the BMR arid MMR were determined in individuals from the northern population of Caleta Loa, and the southern population of La Picada. Individuals front 'La Picada' Population were heavier than those from Caleta Loa. MMR and BMR exhibited higher values in cold acclimated animals compared with warm-acclimated animals. Besides, BMR, but not MMR, was lower in Caleta Loa individuals, in spite of the acclimation treatment. Hence, the differences in the metabolic capacities and the response to acclimation of C. olivaceus populations appear to be an evolutionary response to the environmental cues.