Scaling of brain volume in mammals. A case for complex allometry?

RIERA, MIQUEL; VASSALLO AI; CASINOS, ADRIÀ

Punta del Este

Congreso; 9 International Congress Vertebrate Morphology; 2010

Society Vertebrate Morphology

In order to calculate the scaling of the brain volume to body mass in mammals, we gathered alarge sample of data from the literature. We completed the sample with data from the fossilrecord, where big mammals are particularly abundant. The null hypothesis to test was whetherthe regression coefficients calculated for small and large mammals were different and whetherthey increased with size. Therefore, the sample was divided in two subsamples (small and largemammals) and the corresponding analyses were carried out with a model II of regression. Weperformed the same analysis on different orders of mammals to assure there was nophylogenetic bias on our results. Complementarily, we also gathered a small sample of data onbasic metabolic rates (BMR) and body mass to see whether parallel results to the brain volumeregressions were obtained. Finally it was tested whether the sample fitted a complex allometrymodel. The regression results shown there were differences in the allometry coefficients ofsmall and large mammals, being the coefficient for large mammals higher than that of smallones. In some cases, the isometry prediction was included in the corresponding confidenceintervals. Similar results were obtained at testing some particular mammalian orders. Similarvalues to the regression coefficients of brain volume were calculated for the scaling of thepartitioned sample of BMR to body mass. Regarding the complex allometry test, the sampleseemed to fit the model.Keywords: brain volume; size; allometry