Intraspecific relationships between resting and activity metabolism in anuran amphibians:: Influence of ecology and behavior

The aerobic capacity model, as well as other models for the evolution of aerobic metabolism and the origin of endothermy, requires a mechanistic link between rates of resting and activity oxygen consumption ((V) over dotO(2rest) and (V) over dotO(2 act)). The existence of such link is still controversial, but studies with anuran amphibians support a correlation between (V) over dotO(2 rest) and (V) over dotO(2 act) at both the intraspecific and interspecific levels. Because results at the intraspecific level are based only on a few species, we test for the generality of a link between these two metabolic variables in anurans by studying the intraspecific correlational patterns between mass-independent (V) over dotO(2 rest) and (V) over dotO(2 act) in anurans. We focus on 21 Neotroptical species from different geographical areas that include remarkable diversity in behavior and thermal ecology. Although uncorrelated, (V) over dotO(2 rest) and (V) over dotO(2 act) seem to be consistent among individuals. Diverse intraspecific phenotypic correlational trends were detected, indicating that the intraspecific relationships between (V) over dotO(2 rest) and (V) over dotO(2 act) might be very diverse in anurans. The three possible trends (positive, negative, and absent correlations) were observed and appeared to be predictable from ecological and behavioral variables that relate to evolutionary physiological shifts in anurans. Positive correlations between (V) over dotO(2 rest) and (V) over dotO(2 act) were more common in species with active lifestyles (e.g., intense vocal activity) and in species that call at low temperatures (e.g., winter or high-elevation specialists).