Macrophysiological Patterns in the Energetics of Caviomorph Rodents: Implications in a Changing World

Abstract

. In this article we review literature-based data on energy metabolism of caviomorph species in a changing world. The pioneer work of Arends and McNab (2001) analyzed the energetics of 30 caviomorph species, specifically the effect of their food habits and habitat preferences on basal metabolic rates. We would go further and test for the effect of body mass and geo-climatic factors (latitude, altitude, ambient temperature, precipitation) on caviomorph comparative energetic diversity. We analyze the relationship between changes in basal metabolic rate (BMR) and thermal conductance (Cmin) by using conventional statistics and phylogenetically informed analyses. As this group is so diverse in terms of habitat use and distribution, for instance, we were not able to find any exogenous factor affecting energy metabolism and thermal conductance. Moreover, as the variance of BMR (~96 %) or C min (~85 %) is explained almost entirely by body mass, it is understandable that it is not easy to correlate the residual percentage with geographical or climatic variables. We further discuss the effect of diet (quality, availability, predictability) on caviomorph energetics. As we performed an interspecific analysis (macroevolutionary) to test for correlations between metabolic variables and geo-climatic traits, we did not take into account the individual and/or population variability, then we discuss the proximate factors (i.e., ambient temperature, diet) responsible for differences in the rate of metabolism and thermal conductance and their underlying mechanism in species belonging to this group. Furthermore, we also analyze the cost of different behaviors and activities that influence caviomorph lifestyles. We believe that there is valuable non-basal energetic information available that could be used to understand the whole picture of energy metabolism and thermal biology among caviomorph rodents. There is compelling evidence of climatic warming at a global scale (IPCC 2013). Searching for global patterns of physiologic variables in endotherms is an effort to understand and to predict the scope of these changes. With the available data from caviomorph rodents, we observed that no clear energetic trend appears in this group, because no geo-climatic variable affects patterns of minimal metabolism and thermal conductance. We are far from a complete understanding of the effect of climate change on caviomorph rodents; however, this review is an endeavor in this sense. Certainly, more studies analyzing physiological diversity in different taxonomic groups taking into account large geographic and temporal scales are needed to understand climate change effects. This kind of study must not only consider the predicted increase in ambient temperature, but also it needs to go beyond and search for global-scale patterns in other environmental factors such as photoperiod or seasonal timing. We review physiological information for many caviomorph species; however, for many others, neither physiological nor ecological or genetic information is available. As we outlined, some relevant issues must be taken into account (intraspecific-interpopulation physiological information). As more of this knowledge becomes available, we may be able to predict more accurately the responses of individuals, species or taxa to future changes, and predict as to whether climate change will harm or benefit individuals of a particular species.