Environmental variation and the evolution of large brains in birds
Sayol, Creaf, Cerdanyola Del Vallès, Catalonia, Maspons, Lapiedra, Department Of Organismic, Evolutionary Biology, Harvard University, Cambridge
Species data collection For each species, we also extracted information of the geographical range from BirdLife International (Supplementary Fig. Consequently, we always included body size (log-transformed and extracted from the same specimens for which brains were measured) as a co-variate when we modeled brain size as a response. However, we also re-ran the analysis with relative brain size, estimated as the residuals of a log-log PGLS of brain against body size (Supplementary Fig. In the OUMV models, an additional parameter is estimated: the rate of stochastic motion around the optima (σ2), representing the amount of brain size variation around the phenotypic optimum estimated for each group. We fitted the following OU models: (1) a simple OU model with a single optimum (θ) and the same α and σ2 parameters for all selective regimes (‘OU1’ model), (2) an ‘OUM’ model with different optima, and (3) the same OUM model, but with different σ2 for each category (‘OUMV’).