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-Yáñez2,3,4, Hugo Naya5, Miguel B. Araújo2,3,4 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


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 (TLC), upper critical temperature (TUC) or TNZ breadth (TUCTLC = TNZb) with three ambient temperatures in rodent species.

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

Methods: We used TLC, TUC 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 TLC and TUC, and negatively with TNZb. Species that evolved in cold climates exhibited a greater mass-independent TNZb than species from warmer climates. Species that evolved in cold climates exhibited lower TLC and TUC 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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