title: Environmental variation and the evolution of large brains in birds.
abstract: Environmental variability has long been postulated as a major selective force in the evolution of large brains. However, assembling evidence for this hypothesis has proved difficult. Here, by combining brain size information for over 1,200 bird species with remote-sensing analyses to estimate temporal variation in ecosystem productivity, we show that larger brains (relative to body size) are more likely to occur in species exposed to larger environmental variation throughout their geographic range. Our reconstructions of evolutionary trajectories are consistent with the hypothesis that larger brains (relative to body size) evolved when the species invaded more seasonal regions. However, the alternative-that the species already possessed larger brains when they invaded more seasonal regions-cannot be completely ruled out. Regardless of the exact mechanism, our findings provide strong empirical support for the association between large brains and environmental variability.
authors.affiliation: CREAF, Cerdanyola del Vallès, 08193 Catalonia, Spain.
authors.forename: Ferran
authors.identifier: 0000-0003-3540-7487
authors.initials: F
authors.lastname: Sayol
authors.affiliation: CREAF, Cerdanyola del Vallès, 08193 Catalonia, Spain.
authors.forename: Joan
authors.identifier: 0000-0003-2286-8727
authors.initials: J
authors.lastname: Maspons
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 01238, USA.
authors.forename: Oriol
authors.initials: O
authors.lastname: Lapiedra
authors.affiliation: Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada.
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Iwaniuk
authors.affiliation: Milner Centre of Evolution, Department of Biology &Biochemistry, University of Bath, Bath BA2 7AY, UK.
authors.forename: Tamás
authors.initials: T
authors.lastname: Székely
authors.affiliation: CREAF, Cerdanyola del Vallès, 08193 Catalonia, Spain.|CSIC, Cerdanyola del Vallès, 08193 Catalonia, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Sol
mesh_terms: D025041:Animal Migration; D000818:Animals; D001522:Behavior, Animal; D005075:Biological Evolution; D001717:Birds / Q000033:anatomy & histology* / Q000145:classification / Q000502:physiology; D049628:Body Size; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology; D003071:Cognition; D017753:Ecosystem; D004777:Environment; D008954:Models, Biological; D009929:Organ Size; D010802:Phylogeny; D025341:Principal Component Analysis; D012641:Selection, Genetic; D013045:Species Specificity