Evol Ecol Res 16: 143-152 (2014)     Full PDF if your library subscribes.

Thermal tolerances in rodents: species that evolved in cold climates exhibit a wider thermoneutral zone

Francisco Bozinovic¹, Francisco Ferri-Yáñez^2,3,4, Hugo Naya⁵, Miguel B. Araújo^2,3,4 and Daniel E. Naya⁶

¹Departamento de Ecología and Center of Applied Ecology and Sustainability (CAPES), Facultad de Ciencias Biológicas, Universidad Católica de Chile, Santiago, Chile,  ²Departamento de Biogeografía y Cambio Global, LINCGlobal, Museo Nacional de Ciencias Naturales, Madrid, España,  ³InBIO-CIBIO, Universidad de Évora, Évora, Portugal,  ⁴Imperial College London, Silwood Park Campus, Ascot, Berkshire, UK,  ⁵Instituto Pasteur de Montevideo and Departamento de Producción Animal y Pasturas, Facultad de Agronomía, Universidad de la República, Montevideo, Uruguay and  ⁶Departamento de Ecología y Evolución, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay

Correspondence: F. Bozinovic. Departamento de Ecología, CAPES & LINCGlobal, Universidad Católica de Chile, Santiago 6513677, Chile.
e-mail: fbozinovic@bio.puc.cl

ABSTRACT

Background: Thermal constraints are often invoked to explain animal distributions. Maximum temperatures are less variable in different biomes around the globe than are minimum temperatures. Considerable information is available for mammals about basal metabolic rate and thermal conductance.

Aims: Evaluate the correlation of lower critical temperature (T_LC), upper critical temperature (T_UC) or TNZ breadth (T_UC – T_LC = TNZ_b) with three ambient temperatures in rodent species.

Hypotheses: T_LC, T_UC and TNZ_b should be adjusted by selective processes to the ambient temperature that is most usually experienced by mammal species. TNZ_b should be greater in species inhabiting colder habitats.

Methods: We used T_LC, T_UC data from published studies of 85 species of rodents. We determined the average annual mean, minimum and maximum temperatures across the distribution of each species. Then, using standard least squares regression with body mass as a covariate, we determined the statistical relationships between the physiological variables and the temperatures. We evaluated the effect of phylogeny using a Bayesian Phylogenetic Mixed Model in addition to Bayesian Model Averaging.

Results: Ambient temperatures correlate positively with T_LC and T_UC, and negatively with TNZ_b. Species that evolved in cold climates exhibited a greater mass-independent TNZ_b than species from warmer climates. Species that evolved in cold climates exhibited lower T_LC and T_UC than species from warmer climates. Phylogenetic as well as conventional statistics indicated that there are thermoregulatory constraints across geographic gradients.

Keywords: macrophysiology, energetics, environmental temperature, global ecology, climate change, small mammals.

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