Exploring the functional association between physiological plasticity, climatic variability, and geographical latitude: lessons from land snails

Background: The climatic variability hypothesis states that, as the range of climatic fluctuation experienced by terrestrial animals increases with latitude, individuals at higher latitudes should be more plastic than individuals inhabiting lower latitudes. However, it is unclear whether comparatively high flexibility at higher latitudes is due to the direct effect of climatic variability or to other factors associated with latitude. Aim: To investigate the relationship between phenotypic flexibility, geographical latitude, and climatic variability using a dataset where latitude and climatic variability are inversely related. Methods: We assessed the physiological plasticity to cope with thermal change (10 degree C vs. 20 degree C), at the level of metabolic rate and organ dry weight, in three populations of the brown garden snail (Cornu aspersum): Vina del Mar (33 degree 20'S, 71 degree 32'W), with high temperature and rainfall variability; Concepcion (36 degree 47'S, 73 degree 7'W), with a narrow range of temperature variability and intermediate rainfall variability; and Valdivia (39 degree 38'S, 73 degree 5'W), with low temperature and rainfall variability. Results: Standard metabolic rate was higher at 20 degree C than at 10 degree C, but did not differ between populations. Intestine dry weight did not differ among populations but it was higher at 20 degree C than at 10 degree C, particularly for individuals from the Vina del Mar and Concepcion populations. Hepatopancreas and kidney dry weight differed between populations, which was due to higher values in Vina del Mar at 20 degree C. Conclusions: Flexibility in the weight of the organs analysed changed in a similar fashion to annual temperature variation at each locality, suggesting that, as stated by the climatic variability hypothesis, climatic variability is the main force behind physiological plasticity.