Abstract

During the past 2 decades, interest in interindividual variation in performance traits has increased considerably among physiological ecologists. A great deal of this interest has focused on repeatability studies of physiological traits. One of the most important physiological traits in animals is whole-animal metabolism because it reflects several aspects of an organism's energy budget. However, in order to respond to natural selection (ultimately), this variable should be consistent over most of an individual's life history. We studied energy metabolism (CO2 production, V?CO2) in two of the southernmost populations of Helix aspersa land snails, a cosmopolitan species that colonized most of the human-inhabited world. Our results show that H. aspersa exhibits a relatively lower than expected V?CO2 compared with that described in the few other published studies on this species and that there is no significant difference between populations (Valdivia V?CO2 = 0.21 ± 0.01 mL CO2 h-1; Concepción V?CO2 = 0.20 ± 0.01 mL CO2 h-1; mean body mass = 4.2 g). Repeatability of V?CO2 in land snails was significant and was not statistically different in both populations (Valdivia: t = 0.42; Concepción: t = 0.31). These results suggest that energy metabolism is repeatable and can eventually respond to selection in land snails. We argue that land snails are good, though underutilized, models for evolutionary physiology studies. © 2009 by The University of Chicago. All rights reserved.